Article

Beyond the Motagua and Polochic faults: Active strike-slip faulting along the Western North America–Caribbean plate boundary zone

December 2010
Tectonophysics 496(1):17-27

December 2010
496(1):17-27

DOI:10.1016/j.tecto.2010.10.002

Authors:

Universidad Nacional Autónoma de México

I investigate the role of two strike-slip faults in the tectonics of the western North America–Caribbean plate margin. The Ixcan fault, located in Guatemala north of the Polochic fault, is seismically active, with earthquakes of magnitude up to 5.7 reported recently. Fault-plane solutions along this curvilinear but generally E–W trending fault indicate left-lateral, strike-slip displacement. Several historic earthquakes appear to have taken place along the Ixcan fault since 1728, the largest one being the 1816 event (M=7.5). The NW–SE trending Concordia fault in southeastern Mexico appears to be the site of the great (M=7.6) earthquake of 1902. Isoseismals for this event suggest shallow, left-lateral strike-slip faulting.I propose a seismotectonic model in which both faults are part of the deformation associated to the North America–Caribbean plate boundary zone. Transpressive structures are found in the fault steps between strike-slip fault systems.

Sedimentary architecture, structural setting, and Late Cenozoic depocentre migration of an asymmetric transtensional basin: Lake Izabal, eastern Guatemala

Article

Dec 2018
TECTONOPHYSICS

Lake Izabal, located in eastern Guatemala, lies in an EW-trending basin located along the transform margin between the North American and Caribbean plates. This plate boundary consists of two main left-lateral, strike-slip faults known as the Polochic and Motagua Fault System (PMFS). The basin is a 100 × 20 km lens-shaped depression in which the lake occupies its eastern half. To the north, the basin is confined by a Principal Deformation Zone (PDZ) which is recognized in this area as the most important upper-crustal branch of the Polochic Fault. The eastern part of the basin has been uplifted and dissected, exposing the basin infill along the slopes of the Montaña del Mico. Analysis of a set of multichannel seismic reflection profiles, most of them acquired within the lake, combined with well and outcrop information, allowed to outline the structure and evolution of the basin and its stratigraphic architecture. The basin is strongly asymmetrical, both in cross and along-strike directions, and is filled up by Neogene to Quaternary sediments, with the deepest side of the basin being to the north, close and parallel to the PDZ. The base of the infill is a mid-Tertiary unconformity whose differential subsidence through time brought the basin to its present structural setting. Five main evolutionary stages are recognized based on seismo-stratigraphic and structural features, which are related to the development and activity of the bordering faults. Development of the basin began in its easternmost sector. A small half graben, tilted to the south, developed in response to the activity of an Oligocene (?) or Early-Middle Miocene growth fault. In the second stage (Late Miocene), the basin tilts to the north, causing the sedimentary sequences to thicken towards the northern PDZ. This stage is dominated by oblique extension, and by progressive migration of the basin depocenter towards the west. The third stage (Early Pliocene) records a strong acceleration of the strike-slip activity which causes a rapid westward migration of the depocenter. The fourth stage (Late Pliocene), although still dominated by regional transtension, is related to the development of a transpressional event along the eastern side of the basin, as evidenced by the occurrence of folds and reverse faults parallel to the northern bend of the Polochic Fault. During the fifth stage (Quaternary), the eastern part of the basin remains relatively quiescent while the western part undergoes subsidence with localized transtension, still related to the activity in this sector of the Polochic Fault. Left-lateral movement along the Polochic Fault caused the depocenter to migrate 75–80 km at different velocities, with slip rates ranging between 2.1 and 16.3 mm/yr. This study suggests that the Polochic Fault developed in the Early-Middle Miocene in connection to the deposition of the early sediments of the Izabal Basin, even though an older age (Oligocene?) could also be possible. To our knowledge, this is one of the best examples of sedimentary architecture documenting depocentre migration due to fault movement along a transform system.

New fission-track results from the northern Chiapas Massif area, SE Mexico: Trying to reconstruct its complex thermo-tectonic history

Article

Full-text available

Mar 2018

The Chiapas Massif Complex, which represents the crystalline basement of the southern Maya block within the North American plate, records numerous thermo-tectonic and magmatic events that occurred in southern Mexico at least since the late Mesoproterozoic. The present study was performed across the northern Chiapas Massif region to reconstruct its complex thermo-tectonic history from Mesozoic to present times. Basement samples and sandstones of the San Ricardo Formation derived from the Chiapas Massif Complex source area were analyzed by in situ apatite fission-track dating. The new fission-track results obtained in this study, together with previously published data, indicate that the Chiapas Massif Complex, or rather the whole Maya terrane, have experienced a complex long-term geodynamic evolution with at least five post-Permian tectonic and magmatic events: (1) a Late Triassic cooling event, likely related to the initial breakup of Pangea; (2) Early Jurassic volcanism that can be linked to the Nazas volcanic arc; (3) a Middle Jurassic tectonic event that was triggered by continental rifting at the beginning of the opening of the Gulf of Mexico; (4) a Late Cretaceous to Paleocene orogeny that may actually represent the southernmost continuation of the Laramide sensu lato which affected central and northern Mexico; and (5) the middle–late Miocene Chiapanecan event that is tectonically controlled by the interaction of the North American, Caribbean, and Cocos plates. This interpretation could be useful towards a better understanding of the geological history of southern North America. Some recommendations on sampling and analytical strategies are also given for consideration in further thermochronological studies in Chiapas.

LA-ICP-MS-based apatite fission track dating of the Todos Santos Formation sandstones from the Sierra de Chiapas (SE Mexico) and its tectonic significance

Article

Full-text available

Jun 2015

This study reports the first LA-ICP-MS-based apatite fission track age data from the Toarcian–Oxfordian Todos Santos Formation sandstones exposed in the Sierra de Chiapas (SCH), SE Mexico. Single-grain fission track ages obtained from four rock samples vary between 232 ± 31 (1σ) and 40 ± 3 (1σ) Ma, indicating partial resetting of detrital apatite populations by post-depositional heating during diagenesis. Decomposed data were interpreted as follows: (a) cooling of the sediment source area at 203 ± 7 (1σ) and 163 ± 3 (1σ) Ma, which are respectively coincident with the late Permian–Triassic thermo-tectonic event and Early–Middle Jurassic arc volcanism that affected the Chiapas Massif Complex; and (b) a post-burial cooling period (with variable cooling rates of <3°C Ma–1) in the range of ~83–51 Ma controlled by a Late Cretaceous–early Eocene tectonic activity, which can be correlated with the Laramide orogeny that occurred along central and northern Mexico during the same period of time (i.e. from 85–80 to 50–40 Ma). The results obtained in the present study, as well as previously published data, indicate that the SCH has experienced a multi-episodic thermo-tectonic evolution with at least four main stages.

Tectonically and climatically driven mountain-hopping erosion in central Guatemala from detrital <sup>10</sup>Be and river profile analysis

Article

Full-text available

Jul 2021

The rise of a mountain range affects moisture circulation in the atmosphere and water runoff across the land surface, modifying the distribution of precipitation and drainage patterns in its vicinity. Water routing in turn affects erosion on hillslopes and incision in river channels on surrounding mountain ranges. In central Guatemala, two parallel, closely spaced mountain ranges formed during two consecutive pulses of uplift, the first between 12 and 7 Ma (Sierra de Chuacús–Sierra de las Minas), and the second after 7 Ma (Altos de Cuchumatanes). We explore the climatic and tectonic processes through which the rise of the most recent range drove the slowing of river incision and hillslope erosion over the previously uplifted range. The 40Ar/39Ar dating of perched volcanic deposits documents the sequential rise and incision of these mountain ranges. Terrestrial cosmogenic 10Be in river sediments indicates that currently hillslopes in the older range erode more slowly than in the younger range (20–150 vs. 300 m Myr−1). These differences mimic the current distribution of precipitation, with the younger range intercepting the atmospheric moisture before it reaches the older range. River channel steepness and deformation of paleovalleys in the new range further indicate that the younger range has been rising faster than the older range up to today. We review how atmospheric moisture interception and river long-profile adjustment to the rise of the new range have contributed to the decline of erosion rates over the old range. We also explore the consequences of this decline and of aridification on the topographic evolution of the older range. The older range undergoes a slow topographic decay, dominated by backwearing, by the stacking of slowly migrating erosion waves along the mountain flanks, and by the formation of pediments around its base. The morphology of the old range is therefore transitioning from that of a front range to that of a dry interior range.

Tectonically- and climatically-driven mountain-hopping erosion in Central Guatemala from detrital 10Be and river profile analysis

Preprint

Full-text available

Feb 2021

The rise of a mountain range affects moisture circulation in the atmosphere and water runoff across the land surface, modifying the distribution of precipitation and the shape of drainage patterns. Water routing in turn affects erosion on hillslopes and incision in river channels. The rise of a mountain range thereby alters the erosion of surrounding mountain ranges. We document here such influence in Central Guatemala, where two parallel, closely spaced mountain ranges formed during two consecutive pulses of single-stepped uplift, one from 12 to 7 Ma (Sierra de Chuacús-Sierra de las Minas), and the second one after 7 Ma (Altos de Cuchumatanes). We explore the climatic and tectonic processes by which the rise of the most recent range drove the slowing of river incision and hillslope erosion over the previously-uplifted range. 40Ar-39Ar dating of perched volcanic deposits documents the sequential rise and incision of the two mountain ranges. Terrestrial cosmogenic 10Be in river sediments shows that hillslopes in the older range today erode more slowly than in the younger range (20-150 vs. 300 m∙My-1), and that these differences mimic the current distribution of precipitation, the younger range intercepting the atmospheric moisture before it reaches the older range. River channel steepness and deformation of paleovalleys in the new range further show that the younger has risen faster than the older range up to today. We review how atmospheric moisture interception and river long-profile adjustment to the rise of the new range contribute to the decrease in erosion rates over the old range. We then explore how the topography of the older range has evolved in response to the decrease in erosion rates. The old range undergoes topographic decay, owing to the stalling of river incision around its base. Aridification makes such decay very slow, and dominated by backwearing, rather than downwearing, marked by the stacking of slowly-migrating erosion waves along the mountain flanks, and by the formation of pediments around its base. The morphology of the old range is therefore transitioning from that of a front range to that of a dry interior range.

CCAF-DB: The Caribbean and Central American Active Fault Database

Preprint

Full-text available

Mar 2019

A database of ~250 active fault traces in the Caribbean and Central American regions has been assembled to characterize the seismic hazard and tectonics of the area, as part of the GEM Foundation's Caribbean and Central American Risk Assesment (CCARA) project. The dataset is available in many vector GIS formats, and contains fault trace locations as well as attributes describing fault geometry and kinematics, slip rates, data quality and uncertainty, and other metadata as available. The data is public and open-source (available at https://github.com/GEMScienceTools/central_am_carib_faults), will be updated progressively as new data is available, and is open to community contribution. The active fault data show deformation in the region to be centered around the margins of the Caribbean plate. Northern Central America has sinistral and reverse faults north of the sinistral Motagua-Polochic Fault Zone, which accommodates sinistral Caribbean-North American relative motion. The Central American Highlands extend east-west along a broad array of normal faults, bound by the Motagua-Polochic Fault Zone in the north and dextral faulting in the southwest between the Caribbean plate and the Central American forearc. Faulting in southern Central America is complicated, with trench-parallel reverse and sinistral faults. The northern Caribbean-North American plate boundary is sinistral offshore of Central America, with transpressive stepovers through Jamaica, southern Cuba and Hispaniola. Farther east, deformation becomes more contractional closer to the Lesser Antilles subduction zone, with minor extension and sinistral shear throughout the upper plate, accommodating oblique convergence of the Caribbean and North American plates.

Push-pull driving of the Central America Forearc in the context of the Cocos-Caribbean-North America triple junction

Article

Full-text available

Aug 2019

Different kinematic models have been proposed for the triple junction between the North American, Cocos and Caribbean plates. The two most commonly accepted hypotheses on its driving mechanism are (a) the North American drag of the forearc and (b) the Cocos Ridge subduction push. We present an updated GPS velocity field which is analyzed together with earthquake focal mechanisms and regional relief. The two hypotheses have been used to make kinematic predictions that are tested against the available data. An obliquity analysis is also presented to discuss the potential role of slip partitioning as driving mechanism. The North American drag model presents a better fit to the observations, although the Cocos Ridge push model explains the data in Costa Rica and Southern Nicaragua. Both mechanisms must be active, being the driving of the Central American forearc towards the NW analogous to a push-pull train. The forearc sliver moves towards the west-northwest at a rate of 12–14 mm/yr, being pinned to the North American plate in Chiapas and western Guatemala, where the strike-slip motion on the volcanic arc must be very small.

Western Caribbean intraplate deformation: Defining a continuous and active microplate boundary along the San Andres rift and Hess Escarpment fault zone, Colombian Caribbean Sea

Article

Full-text available

Aug 2018
AAPG BULL

The San Andres rift (SAR), located on the lower Nicaraguan Rise, is a previously poorly studied, active, 015°-trending, bathymetric, and structural rift basin that is 11–27 km (7–17 mi) wide and extends for 346 km (215 mi) across the western flank of the Caribbean plate. In this study, we integrate bathymetric maps, potential field data, and high-resolution, two-dimensional (2-D) seismic lines to understand the crustal structure, tectonic history, and tectonic origin of the SAR, which is one of the active areas within the otherwise stable Caribbean plate. We compiled regional gravity and magnetic data that revealed a negative gravity anomaly and positive magnetic anomaly that we interpret as a result of crustal thinning and an elevated Moho along the main rift axis of the SAR. Forward models of gravity data show four possible interpretations for the origin of the crust underlying and surrounding the SAR. Interpretations of 2-D seismic reflection data show structural features within the upper crust and sedimentary sections typical of other active rift systems including a SAR-parallel, north–south alignment of earthquakes with the larger events showing normal and strike-slip focal mechanisms. Sequential kinematic restorations based on 2-D seismic profiles reveal three major phases of SAR opening: (1) the initial early Eocene rifting stage; (2) middle Eocene extension; and (3) a rapid middle Miocene to early Pliocene extension accompanied by emergence of the San Andres Island as a rift shoulder. We propose slab rollback and intraplate extension as main tectonic mechanisms to explain all rift phases and Neogene volcanism found in the western Caribbean region.

Single-grain apatite geochemistry of Permian–Triassic granitoids and Mesozoic and Eocene sandstones from Chiapas, southeast Mexico: implications for sediment provenance

Article

Full-text available

Feb 2016

This article reports single-grain multi-elemental results (Sr, Y, Th, U, and rare earth elements) obtained in 966 apatites from 18 rocks (sandstones and granitoids) that were sampled from the Mesozoic (Todos Santos and San Ricardo Formations) and Eocene (the El Bosque Formation) successions as well as from the Permian–Triassic Chiapas Massif Complex (CMC), all of which are exposed within the Sierra de Chiapas (SCH), SE Mexico. The objectives of the present study are (1) to establish changes in provenance between the Mesozoic and Eocene sedimentary sequences using single-grain apatite geochemistry, and (2) to identify source areas for siliciclastic materials from the Todos Santos, San Ricardo, and the El Bosque Formations. The results of the present work strongly suggest that apatites from the Todos Santos and San Ricardo Formations were mainly derived from intermediate to felsic I-type granitoids as well as from arc-related volcanic rocks, indicating that the CMC basement was the most important source area for the Mesozoic sandstones in the SCH. An abrupt change in provenance from Mesozoic to Eocene units was identified based on single-grain apatite geochemistry. Detrital apatites of the Ypresian–Lutetian El Bosque Formation were derived from diverse source rocks such as mafic–ultramafic rocks, intermediate to felsic I-type plutons, strongly fractionated S-type granites and pegmatites, as well as from different metamorphic source lithologies (including high-pressure rocks) such as gneisses, migmatites, metapelites, and/or eclogites. It was proposed, therefore, that most Eocene sediments of the SCH were derived from the Guatemala Suture Complex, which involves all the rock types mentioned above. A minor portion of the El Bosque Formation sediments was derived from the CMC area and/or from recycled sandstones from the Mesozoic Todos Santos and San Ricardo Formations. Some advantages and disadvantages of provenance studies based on detrital apatite chemistry were also observed and briefly discussed.

Early and Late Eocene / Oligo–Miocene (!) Petroleum System on the Nicaraguan Rise: Insights from Basin and Three-dimensional Petroleum System Modeling

Chapter

Jan 2015

Late Cretaceous subduction of the continental basement of the Maya block (Rabinal Granite, central Guatemala): Tectonic implications for the geodynamic evolution of Central America

Article

Mar 2013
GEOL SOC AM BULL, GSA Bulletin

The Rabinal Granite is a peraluminous S-type composite pluton formed upon partial melting of a metasedimentary source region that fringes the southernmost North America plate in central Guatemala. It is therefore considered, together with the intruded metasedimentary sequences, to be part of the continental basement of the Maya block. This leucocratic K-feldspar-plagioclase-quartz-muscovite ± biotite granite shows increasing deformation along its southern margin, where it is cut across by the dextral, Late Cretaceous, top-tothe-NE Baja Verapaz shear zone. Although it has been recently dated at 562-453 Ma (isotope dilution-thermal ionization mass spectrometry), the new data presented here, including laser ablation-inductively coupled plasma-mass spectrometry (LAICP-MS) U-Pb and 40Ar-39Ar geochronology and electron-probe mineral chemistry, allow us to more precisely establish the timing of intrusion and metamorphic overprinting of the Rabinal Granite. The zircons dated by LA-ICP-MS indicate a crystallization age of 471 +3/-5 Ma (Early Ordovician), as well as abundant inherited cores with Pan-African and Mesoproterozoic dates. Laser total fusion Ar-Ar analyses of magmatic low-silica muscovite (Si = 6.2-6.4 atoms per formula unit) indicate cooling following magmatic crystallization during the mid-late Paleozoic and variable extents of resetting of Ordovician micas during Cretaceous metamorphism and deformation. The pressure-temperature (P-T) conditions of the inferred Ordovician metamorphism that produced partial melting of the metasedimentary source of the Rabinal Granite and the ascent and crystallization of the granitic melt are uncertain, but a clockwise P-T-time path with maximum P and T of <8 kbar and 750 °C, respectively, is proposed. A second thermal event is recognized in recrystallized high-silica muscovite (Si up to = 6.8 atoms per formula unit) formed at peak P and T of ~8.5 kbar and ~300 °C, respectively. This second event, dated at 70.1 ± 0.6 Ma by means of laser total fusion 40Ar-39Ar analyses on high-Si muscovite grains, is interpreted to be the result of subduction and accretion of the basement of the Maya block during the latest Cretaceous, likely in a transpressional tectonic regime related to the lateral collision of the Maya block with the Pacific (Farallon)-derived Caribbean arc. This finding represents the first direct evidence for latest Cretaceous subduction of the metamorphic Paleozoic basement of the Maya block, north of the Baja Verapaz shear zone.

A geodynamical perspective on the subduction of Cocos and Rivera plates beneath Mexico and Central America

Article

Full-text available

Jan 2013
TECTONOPHYSICS

The Middle America subduction zone (MASZ) is one of the world’ most complex convergent margins as it involves the subduction of the Rivera and Cocos young oceanic plates beneath the North American and Caribbean plates and is bounded by the Gulf of California rift and the Panama slab window. Characterized by contorted and unusual slab geometry, irregularly distributed seismicity and volcanism, exceptionally large slow slip events (SSE) and non-volcanic tremors (NVT), this subduction system represents a great natural laboratory for better understanding geodynamic processes at a fundamental level. Based on a solid observational foundation, and incorporating the latest experimental results into a coherent geodynamical framework, we shed light on the main processes controlling the subduction system evolution in this region. The tectonics, volcanism, slab geometry and segmentation along the margin are reviewed from a geodynamical perspective. We proposed and discussed a series of evolutionary scenarios for the Mexican and Central American subduction zones, providing a coherent starting base for future geodynamical modeling studies tailored to this active margin. We discuss comparatively the recently discovered SSEs and NVTs along the MASZ, and try to differentiate among the proposed mechanisms responsible for these observations. Finally we discuss the recent seismic anisotropy observations in a geodynamic context, offering an integrated view of mantle flow pattern along the entire active margin. Although the MASZ as a whole may be considered a fairly complicated region with many unusual features and sometimes controversial interpretations, its complexity and unusual characteristics can improve our knowledge about the linkage between deep and surface processes associated with subduction zone dynamics.

Zonificación de la Ciudad de Guatemala

Conference Paper

Full-text available

Sep 2021

Derived from previous studies carried out in Guatemala City [Matus, M. (1994); Ligorría, J. & Akatan, K. (1997); Flores, O. et al. (2001); JICA-INSIVUMEH (2003); Cosenza, B. et al. (2015)], began with updating the Seismic Zoning of Guatemala City by analyzing the environmental noise generated on the ground, through the Nakamura method or H / V spectral relationship, and by dispersing shear waves, using multichannel analysis of surface waves (MASW). From 23 study stations, we proceeded to calculate three fundamental parameters that govern the local effects that earthquakes can produce: the fundamental period of vibration, the resonance frequency and the shear wave velocity (Vs). Once these parameters were calculated, the soil vibration period map was generated for Guatemala City, the shear wave velocity map (Vs) for 30 meters of depth and seismic hazard maps were generated from a probabilistic method obtained with the macroseismic catalog of Guatemala from the RIESCA project (2018).

Deformation in Western Guatemala Associated With the NAFCA (North America‐Central American Forearc‐Caribbean) Triple Junction: Neotectonic Strain Localization Into the Guatemala City Graben

Article

Full-text available

Feb 2022
TECTONICS

Recent structural and geodetic data define the Guatemala City graben region as the continental triple junction between the North American plate, Caribbean plate, and the Central American Forearc sliver. We present minor fault analysis, geochronological and geochemical analyses, and newly updated GPS velocities in western Guatemala, west of the Guatemala City graben, to characterize the magnitude and timing of extensional deformation in this poorly understood area. Elongations estimated from fault data are parallel (∼east‐west) and perpendicular to the Polochic‐Motagua fault system to the north, similar to geodetically measured active deformation observed east of the Guatemala City graben. Four new ⁴⁰Ar/³⁹Ar dates and correlation of tephra deposits suggest that faulting was active during the Pliocene, but ceased eastward toward the Guatemala City graben over time. From west to east, fault cessation occurred before the deposition of the Los Chocoyos ash (75 ka) and E tephra (51 ka). Faulting just west of the Guatemala City graben appears to be active, where a major fault cuts the most recent Amatitlán tephras. Based on this data, we propose a time‐progressive strain model for deformation related to North America‐Caribbean plate interactions, whereby distributed elongation of the westernmost Caribbean plate occurred during the Pliocene but localized mostly within the Guatemala City graben and nearby faults during the Pleistocene. Our model supports that: (a) The Guatemala City graben is effectively the western limit of the Caribbean plate; and (b) Western Guatemala, which was the trailing edge of the Caribbean plate, has been transferred to the forearc region.

Metodología para el cálculo de acelerogramas sintéticos utilizando funciones de transferencia empíricas y el método estocástico de Boore, en la ciudad de Tapachula, Chiapas

Article

Full-text available

Sep 2019

The main objective of this article is to estimate the synthetic accelerograms of an earthquake with a magnitude of 7.3 in the City of Tapachula, Chiapas, which ocurred on november 7, 2012 on the coasts of Guatemala. In this paper, the methods of the Empirical Transfer Functions and the Boore's Stochastic Method (1983, 2003), which is useful to simulate the high frequency ground motions (f>0.1 Hz), were combined. This is of great interest in the field of engineering (Boore, 2003). The accelerograms were obtained through the method used in this work. In order to verify the degree of adjustment between them, the metrics proposed by Anderson (2004) were used. To accomplish this, tests were performed with known accelerograms recorder in a temporary network. These were installed from June 15 to July 29, 2011, in the City of Tapachula, and were compared later with the synthetic results obtained after applying the mentioned method. For the simulation of a magnitude 4.7 earthquake, both horizontal components showed good adjustment in most of the stations where they were registered. In other words, the method proposed manages to closely approximate the real data recorded in each of the stations. This fact supports the confidence we have in this method, in how particularly useful it is to generate applications of interest in seismic engineering.

Definition of tectonic elements in Tehuantepec, southeast Mexico: An integrated geophysical, geochronological, and stratigraphic perspective

Chapter

Nov 2020

We redefine the "Chontal arc" of the southern Isthmus of Tehuantepec, Mexico, as the Chontal allochthon. The Chontal assemblage is composed of Upper Creta-ceous low-grade metavolcanic and metasedimentary rocks included in the Chivela lithodeme. By means of field observations, laser-ablation detrital zircon geochronol-ogy, and trace-element geochemistry, we constrained the provenance and tectonic setting of these rocks. We concluded that they form an allochthon emplaced during a Paleogene transpressive event. Basement structure in the greater Oaxaca-Chiapas area was assessed by qualitative interpretation of Mexican State aeromagnetic maps. Chivela lithodeme sediments include a contribution from Albian-Turonian volcanic arc rocks no longer present in the region, likely sourced from the Chortís block or from the Greater Antilles Arc as it collided with southern Yucatan. Maastrichtian basic intrusive units, basalt flows, and pillow lavas with pelagic sediments in the Chon-tal are subalkaline, plotting in the normal mid-ocean-ridge basalt (N-MORB) field of discrimination diagrams. The igneous rocks are interpreted as pertaining either to the inception of the paleo-Motagua fault zone (left step in the fault trace), or to local

Neoproterozoic extension and the Central Iapetus Magmatic Province in southern Mexico – New U-Pb ages, Hf-O isotopes and trace element data of zircon from the Chiapas Massif Complex

Article

Full-text available

Aug 2020
GONDWANA RES

Final fragmentation of Rodinia occurred during the Ediacaran Period as Amazonia, Baltica and Laurentia drifted apart to form the Iapetus Ocean. Accompanying rift-related mafic dyke swarms of the Central Iapetus Magmatic Province (CIMP) were emplaced between 0.62 and 0.55 Ga, which are preserved in Laurentia and Baltica, whereas no coeval mafic rocks are known from Amazonia. First evidence for the CIMP extending into Oaxaquia (Rodinia-type basement of Mexico) was reported as tholeiitic dykes that intruded the Novillo gneiss, NE Mexico, at 619 ± 9 Ma. In Chiapas, SE Mexico, amphibolite dykes that are chemically similar to the Novillo dykes intruded anorthosite and gneiss. In this paper, a new dating approach to obtain mafic dyke intrusion ages is presented by targeting contact metamorphic zircon with the U-Pb method, employing Secondary Ion Mass Spectrometry. Zircon that crystallized in anorthosite at intrusive contacts to mafic dykes and at temperatures exceeding 700°C (Ti-in-zircon thermometry) yields ages between 615 ± 7 Ma and 608 ± 12 Ma, reflecting the time of dyke intrusion. Zircon chemical and isotopic (Hf, O) characteristics suggest a diachronous sequence of metamorphic processes involving Zr release from Fe-Ti oxides, breakdown and recrystallization of other phases, and fluid-mitigated reactions during Ordovician metamorphism. Zircon δ18O values of granulites from Oaxaquia range from +6.2‰ to +9.8‰, whereas Tonian (~0.92 Ga) metamorphic zircon from SE Chiapas yielded low δ18O values from +2.0‰ to +2.8‰ that are explained by the reactivation of major tectonic boundaries during Tonian gravitational collapse. The observations increase the known extent of the CIMP in Mexico, suggesting that a Neoproterozoic superplume was still active during the Early Ediacaran producing a Large Igneous Province that extended over Amazonia, Baltica and Laurentia. The results further suggest that Oaxaquia at the northern edge of Amazonia formed the conjugate margin of Baltica during rifting.

A new species of Lophiaris (Orchidaceae, Oncidiinae) from Quiché, Guatemala, in the L. straminea complex

Article

Full-text available

Aug 2020

A new species of Lophiaris (Orchidaceae, Onciidinae), Lophiaris quichensis Coxic, Cetzal, Mó & Carnevali, from the department of Quiché, Guatemala, is herein described, illustrated, and characterized based on morphological features. It is here referred to the L. straminea complex (along with L. aurisasinorum, L. sierracaracolensis, and L. straminea) from which it is easily distinguished by the color of the flowers: sepals and petals yellow, and the whole surface covered with pale reddish-brown spots, the claws with a pale reddish-brown stain, the labellum yellow with a reddish-brown blotch covering the central portion of the central lobe, the disc and partially the teeth of the callus, the lateral lobes with a brown spot at the base of the same. The etymology, distribution, ecology, and comparative differences of the new species with respect to other species of L. straminea complex are discussed. We also provide a comprehensive key to identify the species of L. straminea complex. The conservation status of L. quichensis is assessed as CR by the IUCN criteria.

CCAF-DB: the Caribbean and Central American active fault database

Article

Full-text available

Mar 2020
NAT HAZARD EARTH SYS

A database of ∼250 active fault traces in the Caribbean and Central American regions has been assembled to characterize the seismic hazard and tectonics of the area, as part of the Global Earthquake Model (GEM) Foundation's Caribbean and Central American Risk Assessment (CCARA) project. The dataset is available in many vector GIS formats and contains fault trace locations as well as attributes describing fault geometry and kinematics, slip rates, data quality and uncertainty, and other metadata as available. The database is public and open source (available at: https://github.com/GEMScienceTools/central_am_carib_faults, last access: 23 March 2020), will be updated progressively as new data become available, and is open to community contribution. The active fault data show deformation in the region to be centered around the margins of the Caribbean plate. Northern Central America has sinistral and reverse faults north of the sinistral Motagua–Polochic fault zone, which accommodates sinistral Caribbean–North American relative motion. The Central Highlands in Central America extend east–west along a broad array of normal faults, bound by the Motagua–Polochic fault zone in the north and trench-parallel dextral faulting in the southwest between the Caribbean plate and the Central American forearc. Faulting in southern Central America is complicated, with trench-parallel reverse and sinistral faults. The northern Caribbean–North American plate boundary is sinistral off the shore of Central America, with transpressive stepovers through Jamaica, southern Cuba and Hispaniola. Farther east, deformation becomes more contractional closer to the Lesser Antilles subduction zone, with minor extension and sinistral shear throughout the upper plate, accommodating oblique convergence of the Caribbean and North American plates.

GPS constraints on deformation in northern Central America from 1999 to 2017, Part 2: Block rotations and fault slip rates, fault locking and distributed deformation

Article

Aug 2019

We describe a new elastic-kinematic model for the present tectonics of northern Central America and southern Mexico, where the Motagua-Polochic fault zone, Middle America subduction zone and faults in the Central America volcanic arc pose significant seismic hazards. The new model, which consists of the angular velocities for eight plates and blocks, interseismic locking solutions for some of the block-bounding faults and strain-rate tensors for three blocks with significant internal deformation, optimizes the fit to regional fault azimuths and earthquake slip directions and a new 200+ station GPS velocity field that has been corrected for the coseismic and post-seismic effects of three large regional earthquakes in 2009 and 2012. From our new observations and modelling thereof, we find evidence for the following: (1) 13±1 mm yr−1 of ≈E-W stretching between undeformed Caribbean plate in central Honduras and a location ≈50 km west of the Guatemala City graben; (2) accommodation of the above extension via slow W-to-WNW motions of newly defined Chortis and Ipala blocks and distributed ENE-WSW stretching within both blocks; (3) 80 per cent of Chortis-North America plate motion in eastern Guatemala occurs on the Motagua fault versus only 20 per cent on the Polochic fault; (4) Motagua fault slip rates that decrease westwards from 14 ± 1.5 mm yr−1 to 9–10 ± 2 mm yr−1 to less than 2 mm yr−1 in eastern Guatemala, central Guatemala and west of the Guatemala City graben, respectively; (5) Slip rates along Central America volcanic arc faults that decrease from 12.5 ± 1.0 mm yr−1 in Nicaragua to 10 ± 1.3 mm yr−1 in central El Salvador to 7.6 ± 2.1 mm yr−1 on the Jalpatagua fault of southern Guatemala to 2-3 mm yr−1 or less across the volcanic arc west of Guatemala City; (6) a transition near the Mexico–Guatemala border from moderate-to-high locking of the subduction interface offshore from southern Mexico to low locking below the Central America forearc sliver; (7) Subduction of the Cocos plate beneath the Central America forearc sliver up to 10 mm yr−1 faster than and 7–8◦ clockwise from all previous estimates; (8) 12 ± 6 mm yr−1 of E–W extension across the newly defined Fonseca block. A pattern of misfits to the velocities of sites in northern Guatemala and southern Mexico may be caused by distributed deformation in this region or shortcomings with our model and/or assumptions. The primary factors that control the regional deformation appear to include the arcuate geometry of the Motagua fault, low locking of the Middle America subduction interface, slow-to-no motion between the leading edge of the Central America forearc sliver and North America plate and a rheologically weak volcanic arc.

Seismic hazard at a triple plate junction: the state of Chiapas (México)

Article

Full-text available

Jul 2019
NAT HAZARDS

The state of Chiapas (SE México) conforms a territory of complex tectonics and high seismic activity. The interaction among the Cocos, North American and Caribbean tectonic plates, as well as the active crustal deformation inside Chiapas, determines a variety of seismogenic sources of distinct characteristics and particular strong ground motion attenuation. This situation makes the assessment of seismic hazard in the region a challenging task. In this work, we follow the methodology of probabilistic seismic hazard analysis, starting from the compilation of an earthquake catalogue, and the definition of seismogenic source-zones based on the particular seismotectonics of the region: plate-subduction-related sources (interface and intraslab zones), active crustal deformation zones and the shear zone between the North American and Caribbean plates formed by the Motagua, Polochic and Ixcán faults. The latter source is modelled in two different configurations: one single source-zone and three distinct ones. We select three ground motion prediction equations (GMPEs) recommended for South and Central America, plus two Mexican ones. We combine the GMPEs with the source-zone models in a logic tree scheme and produce hazard maps in terms of peak ground acceleration and spectral acceleration for the 500-, 1000- and 2500-year return periods, as well as uniform hazard spectra for the towns of Tuxtla Gutiérrez, Tapachula and San Cristóbal. We obtain higher values in comparison with previous seismic hazard studies and particularly much higher than the output of the Prodisis v.2.3 software for seismic design in México. Our results are consistent with those of neighbouring Guatemala obtained in a recent study for Central America.

Guatemala paleoseismicity: From Late Classic Maya collapse to recent fault creep

Article

Full-text available

Oct 2016

Open access link: http://rdcu.be/mERv We combine 'on-fault' trench observations of slip on the Polochic fault (North America-Caribbean plate boundary) with a 1200 years-long 'near-fault' record of seismo-turbidite generation in a lake located within 2 km of the fault. The lake record indicates that, over the past 12 centuries, 10 earthquakes reaching ground-shaking intensities ≥ VI generated seismo-turbidites in the lake. Seismic activity was highly unevenly distributed over time and noticeably includes a cluster of earthquakes spread over a century at the end of the Classic Maya period. This cluster may have contributed to the piecemeal collapse of the Classic Maya civilization in this wet, mountainous southern part of the Maya realm. On-fault observations within 7 km of the lake show that soils formed between 1665 and 1813 CE were displaced by the Polochic fault during a long period of seismic quiescence, from 1450 to 1976 CE. Displacement on the Polochic fault during at least the last 480 years included a component of slip that was aseismic, or associated with very light seismicity (magnitude <5 earthquakes). Seismicity of the plate boundary is therefore either non-cyclic, or dominated by long-period cycles (> 1 ky) punctuated by destructive earthquake clusters.

The Rationale and Essential Elements for the New ‘Pirate’ Model of Caribbean Tectonics

Article

Apr 2013
GEOSCI CAN

Fraser Keppie

Geology of the coastal Chiapas (Mexico) Miocene plutons and the Tonalá shear zone: Syntectonic emplacement and rapid exhumation during sinistral transpression

Article

Full-text available

Mar 2015

Late Miocene plutons in coastal Chiapas, Mexico, represent the roots of an extinct magmatic arc. Miocene granitoids of calc-alkaline composition and arc chemistry intruded into and were deformed within the Tonalá mylonite belt in the middle to upper crust. The mylonite belt is a crustal-scale shear zone extending along the western margin of the Chiapas Massif for ~150 km. Deformation is characterized by a dominantly subhorizontal lineation and subvertical foliation along a strikingly linear zone that trends ~310°. Mylonitic fabrics contain ambiguous but dominantly sinistral shear indicators. Intrusions are interpreted as syntectonic on the basis of similar U-Pb zircon crystallization age estimates (ca. 10 Ma) and the cooling age estimates obtained on neoformed micas in the mylonite. The plutons are elongated, their long axis is parallel to shear zone, and some plutons show markedly asymmetric outcrop patterns, with sheared tails that trail behind the intrusions and that are consistent with sinistral displacement. Parts of plutons were mylonitized by continuous deformation in the Tonalá shear zone, locally developing intricate pseudotachylyte and cataclasite veins slightly oblique to the mylonite foliation. Outside of the shear zone, plutons preserve magmatic fabrics. These observations are consistent with features common to syntectonic granites interpreted to have been emplaced along strike-slip shear zones in a transpressional setting. We interpret the Tonalá mylonites as representing a relict transform boundary that was slightly oblique to the Polochic-Motagua fault system, which accommodated over 100 km of sinistral displacement between the Chortis block (on the Caribbean plate) and Chiapas (on the North America plate) in late Miocene time.

Kinematic reconstruction of the Caribbean region since the Early Jurassic

Article

Full-text available

Nov 2014
EARTH-SCI REV

The Caribbean oceanic crust was formed west of the North and South American continents, probably from Late Jurassic through Early Cretaceous time. Its subsequent evolution has resulted from a complex tectonic history governed by the interplay of the North American, South American and (Paleo-)Pacific plates. During its entire tectonic evolution, the Caribbean plate was largely surrounded by subduction and transform boundaries, and the oceanic crust has been overlain by the Caribbean Large Igneous Province (CLIP) since ~ 90 Ma. The consequent absence of passive margins and measurable marine magnetic anomalies hampers a quantitative integration into the global circuit of plate motions. Here, we present an updated, quantitatively described kinematic reconstruction of the Caribbean region back to 200 Ma, integrated into the global plate circuit, and implemented with GPlates free software. Our reconstruction includes description of the tectonic units in terms of Euler poles and finite rotation angles. Our analysis of Caribbean tectonic evolution incorporates an extensive literature review. To constrain the Caribbean plate motion between the American continents, we use a novel approach that takes structural geological observations rather than marine magnetic anomalies as prime input, and uses regionally extensive metamorphic and magmatic phenomena such as the Great Arc of the Caribbean, the CLIP and the Caribbean high-pressure belt as correlation markers. The resulting model restores the Caribbean plate back along the Cayman Trough and major strike-slip faults in Guatemala, offshore Nicaragua, offshore Belize and along the Northern Andes towards its position of origin, west of the North and South American continents in Early Cretaceous time. We provide the paleomagnetic reference frame for the Caribbean region by rotating the Global Apparent Polar Wander Path into coordinates of the Caribbean plate interior, Cuba, and the Chortis Block. We conclude that formation of the Caribbean plate, west of the North and South Americas, as a result of Panthalassa/Pacific spreading leads to a much simpler plate kinematic scenario than Proto-Caribbean/Atlantic spreading. Placing our reconstruction in the most recent mantle reference frames shows that the CLIP originated 2000-3000 km east of the modern Galápagos hotspot, and may not have been derived from the corresponding mantle plume. Finally, our reconstruction suggests that most if not all modern subduction zones surrounding the Caribbean plate initiated at transform faults, two of these (along the southern Mexican and NW South American margins) evolved diachronously as a result of migrating trench-trench-transform triple junctions.

Petrology of two contrasting Mexican volcanoes, the Chiapanecan (El Chichón) and Central American (Tacaná) volcanic belts: The result of rift- versus subduction-related volcanism

Article

Full-text available

Oct 2014

The alkaline El Chichón and calc-alkaline Tacaná volcanoes, located in southern Mexico, form parts of the Chiapanecan Volcanic Belt and Central American Volcanic Arc, respectively. El Chichón has emitted potassium-, sulphur-, and phosphorus-rich trachyandesites and trachybasalts (as mafic enclaves), whereas Tacaná has erupted basalts to dacites with moderate potassium contents, and minor high-Ti magmas (1.5–1.8 wt.% TiO2). The magmatic evolution in the two volcanoes has involved similar fractionating assemblages: Fe-Ti oxides, olivine, plagioclase, pyroxenes, amphibole, and apatite. K2O/P2O5 ratios and isotopic signatures indicate that magmas from both El Chichón and Tacaná have undergone significant crustal contamination. The volcanism at both Tacaná and El Chichón was previously related to northeastward subduction of the Cocos Plate, representing the main arc and the backarc, respectively. Although such an origin is in accord with Tacaná occurring 100 km above the Cocos Benioff Zone, it is inconsistent with: (a) the absence of a calc-alkaline belt between El Chichón and the Middle America Trench; and (b) truncation of the subducted Cocos Plate by the southwesterly dipping Yucatan slab near the Middle America Trench (i.e. the Cocos Plate does not presently underlie El Chichón). On the other hand, El Chichón and the Chiapanecan Volcanic Belt are located on the sinistral Veracruz fault zone that forms the northern boundary of the Southern Mexico block, which has been migrating relatively to the east since ca. 5 Ma. In this context, the anomalous high potassium, sulphur, and phosphorus levels in the El Chichón magmas are explicable in terms of rifting in a pull-apart system with the weak subduction fingerprint inherited from the Yucatan slab.

Late Cenozoic migration of the Caribbean-North America-Cocos triple junction: the zipper and pull-up models (Guatemala)

Article

Full-text available

Apr 2013

Our study deals with the crustal deformation produced by the migration of a triple plate junction implying a subduction zone and a transform fault system separating two continental plates. We have chosen the Caribbean-North America-Cocos triple junction as a case study. The Polochic-Motagua fault system are part of the sinistral transform boundary between the North American and Caribbean plates. To the west, these system interact with the subduction zone of the Cocos plate. The linearity of the subduction zone is explained by a mechanically strong oceanic plate that does not tear in the triple junction implying intra-continental deformation. Structural and geomorphic data allow us to propose two tectonic models involving the progressive capture of southern North American blocks by the trailing edge of the Caribbean plate (pull-up tectonics) and a progressive suturing of fault-bounded blocks to the trailing edge of the Caribbean plate associated with a continuous forearc sliver along the two continental plates (zipper model). As a result, the forearc sliver helps maintain a linear subduction zone along the trailing edge of the Caribbean plate. The Late Quaternary activity of the Polochic transform fault have been constrained by determining the active structure geometry and quantifying recent displacement rates. Slip rates have been estimated from offsets of Quaternary volcanic markers and alluvial fan using in situ cosmogenic 36Cl exposure dating. Holocene left-lateral slip rate and Mid-Pleistocene vertical slip-rate have been estimated to 4.8 ± 2.3 mm/y and 0.3 ± 0.06 mm/y, respectively, on the central part of the Polochic fault. The non-negligible vertical motion participates in the uplift of the block north of the fault in agreement with the proposed pull-up model.

Geothermal asymmetry across a continental transform fault inferred from thermochronology: the Motagua Fault Zone, Guatemala

Article

Full-text available

Apr 2013

Strike-slip faults juxtapose crustal blocks with different geodynamic origins and potentially different thermal structures. Large-magnitude horizontal displacements along these faults may juxtapose terranes of contrasted thermal regimes. The effect of strike-slip faulting on the cooling histories that are derived from thermochronological dating remains poorly documented. We have used the zircon (U-Th)/He method in order to construct age-elevation profiles across the Motagua fault zone, a 500 km-long segment of the transform boundary between the North American and Caribbean plates. We combine our results with published thermochronological data to document a sharp cooling age discontinuity across the Motagua fault. This discontinuity could be interpreted as a difference in denudation history on each side of the fault. However, a low-relief Miocene erosional surface extends across the fault; this surface has been uplifted and incised and provides a geomorphic argument against differential denudation across the fault. Using surface heat-flow data, thermochronological age-elevation profiles and three-dimensional thermo-kinematic modeling, we propose that strike-slip displacement has juxtaposed the cold Maya block (s.s.) to the north against the hot, arc-derived, Chortís block (s.s.) to the south. Large-scale horizontal displacement along the Motagua fault maintained this geothermal asymmetry across the fault and explains both the age discontinuities and the age-elevation patterns. This study illustrates how thermochronology can be used to detect large strike-slip displacements.

Preservation of contrasting geothermal gradients across the Caribbean-North America plate boundary (Motagua Fault, Guatemala)

Article

Full-text available

Jul 2013

1] Strike-slip plate boundaries juxtapose crustal blocks that may have different geodynamic origins and therefore different thermal structures. Thermo-kinematic modeling of this type of strike-slip plate boundary predicts an asymmetric signature in the low-temperature thermochronologic record across the fault. Age-elevation profiles of zircon (U-Th)/He ages across the Motagua Fault, a 500 km-long segment of the transform boundary between the North American and Caribbean plates, document a sharp cooling age discontinuity across the fault. This discontinuity could be interpreted as a difference in denudation history on each side of the fault. However, a low-relief Miocene erosional surface extends across the fault; this surface has been uplifted and incised and provides a geomorphic argument against differential denudation across the fault. By integrating magmatic, volcanic, and heat-flow data, age-elevation profiles, and thermo-kinematic modeling, we propose that large horizontal displacement along the Motagua Fault has offset a persistent geothermal asymmetry across the fault and explains both the age discontinuities and the age-elevation patterns. This study illustrates how thermochronology can be used to detect large strike-slip displacements and more generally opens new perspectives in understanding the impact of non-uniform thermal structures on thermochronologic results.

Empirical Earthquake Source Scaling Relations for Maximum Magnitudes Estimations in Central America

Article

Feb 2024
B SEISMOL SOC AM

Central America is a seismically active region where six tectonic plates (North America, Caribbean, Cocos, Nazca, Panama, and South America) interact in a subduction zone with transform faults and two triple points. This complex tectonic setting makes the maximum magnitude-M max-estimation a challenging task, with the crustal fault earthquakes being the most damaging in the seismic history of Central America. The empirical source scaling relations (ESSR) allow the Mmax of faults to be determined from rupture parameters. In this study, we use a dataset of well-characterized earthquakes in the region, comprising 64 events from 1972 to 2021 with magnitudes between M w 4.1 and 7.7. The dataset incorporates records of rupture parameters (length, width, area, slip, and magnitude) and information on the faults and aftershocks associated. This database is an important product in itself, and through its use we determine which global relations fit best to our data via a residual analysis. Moreover, based on the best-quality records, we develop scaling relations for Central America (CA-ESSR) for rupture length, width, and area. These new relations were tested and compared with recent earthquakes, and logic trees are proposed to combine the CA-ESSR and the best-fit global relations. Therefore, we estimate the Mmax for 30 faults using the logic tree for rupture length, considering a total rupture of the fault and multifault scenarios. Our results suggest that in Central America rupture areas larger than other regions are required to generate the same magnitudes. We associate this with the shear modulus (μ), which seems to be lower (∼ 30% less) than the global mean values for crustal rocks. Furthermore, considering multifault ruptures, we found several fault systems with potential Mmax ≥ M w 7.0. These findings contribute to a better understanding of regional seismotec-tonics and to the efficient characterization of fault rupture models for seismic hazards.

The pattern of brittle deformation in Central America for an assessment of the seismo-tectonic framework

Article

Dec 2023
J MAPS

Isótopos, fraccionamiento isotópico y Termodinámica. In R. Soto Ayala et al (eds) Termodinámica para Ciencias de la Tierra: fundamentos y Aplicaciones. Facultad de Ingeniería, UNAM. México

Chapter

Full-text available

Jun 2023

Exhumation and topographic evolution of the Chiapas Massif Complex (southern Mexico) constrained by thermochronologic data modeling along vertical profiles

Article

Jun 2023
GLOBAL PLANET CHANGE

https://www.sciencedirect.com/science/article/abs/pii/S0921818123001327 Thermochronometry is used to better understand the processes responsible for Cenozoic magmatism and exhumation of the Chiapas Massif Complex that spans a diffuse triple junction between the Caribbean, North American and Cocos plates. A combination of zircon U-Pb, apatite fission tracks, (U-Th)/He as well as numerical modeling show contrasting histories. Exhumation started earlier in the south (~16 Ma) relative to the north (~9 Ma). Northern exhumation is related to activity on the Tonalá fault system, while to the south it may be correlated with transpressive deformation in Chiapas fold-and-thrust belt. The southern block also experienced significant topographic growth from ~5 Ma to ~1 Ma followed by intense erosion. Overall, the pattern of uplift is in agreement with the ‘closing zipper’ model in which a forearc sliver is progressively incorporated to the North American plate. Thermal models also support a Pleistocene decrease in topography consistent with independent paleoenvironmental and geomorphologic evidences.

Thermochronological Constraints on the Cenozoic Deformation History of the Chiapas Massif Complex (Southern Mexico)

Article

Jan 2022

Análisis y propuesta de relaciones empíricas de escalamiento de magnitudes para el potencial sísmico de fallas en América Central

Thesis

Full-text available

Jul 2022

Mario Arroyo-Solórzano

América Central es una región sísmicamente activa donde interactúan cinco placas tectónicas (Norteamérica, Caribe, Coco, Nazca y Sudamérica) y la microplaca de Panamá, en una zona de subducción con fallas transformantes y cercana a puntos triples. Este entorno tectónico complejo hace que la estimación del potencial sísmico (magnitud máxima) sea una tarea muy importante. Existen una serie de fórmulas empíricas mediante las cuales se puede estimar el potencial de las fallas a partir de parámetros geométricos de ruptura de terremotos. En este estudio se hizo uso de estas fórmulas para aproximar la magnitud de sismos importantes ocurridos en la región, comparando magnitudes estimadas con las observadas instrumentalmente. Además, se proponen leyes de escalamiento propias para América Central, con base en el conjunto de datos más completo de terremotos relevantes generados por fallas corticales y mejor caracterizados en la región. La base de datos se compone de 64 terremotos ocurridos en América Central entre 1972 y el 2021, con magnitudes entre 4.1 y 7.7 Mw. Este catálogo de sismos consiste en una recopilación de los parámetros de ruptura relativamente bien establecidos de cada terremoto (longitud, ancho, área, deslizamiento, magnitud) y características (ubicación, posible falla asociada, así como las réplicas relacionadas). Los registros de esta base de datos fueron categorizados siguiendo un esquema de pesos, de acuerdo con: 1) el año de ocurrencia, 2) la literatura disponible, 3) la cantidad réplicas tempranas, 4) el conocimiento de la falla asociada y 5) la magnitud del sismo. Con base en esto, se analizaron 19 relaciones empíricas desarrolladas a nivel mundial, y se seleccionaron 13 de ellas para evaluar cuales estiman de mejor manera las magnitudes para el contexto tectónico de América Central. La evaluación de la precisión del ajuste ha sido determinada por medio de un esquema basado en valores estadísticos de: promedio, mediana, error medio cuadrático y error estándar de los residuales, determinando cuatro categorías (A, B, C y D), donde A son las ecuaciones con mejores condiciones y D los que poseen peores ajustes. Los resultados de los ajustes son sintetizados en árboles lógicos para el uso de las distintas relaciones de escalamiento de magnitudes de terremotos (REMT) por cada parámetro de ruptura, los cuales se recomiendan para los futuros análisis de amenaza sísmica en la región. Para los parámetros de ruptura de más amplio uso (longitud y área de ruptura), se recomienda el uso de la ecuación de Thingbaijam et al. (2017), siendo esta la que mejores ajustes presenta con respecto a los datos observados. Esta relación estima áreas de ruptura y valores de aspect ratio considerablemente mayores a otras, como, por ejemplo, las desarrolladas con registros de terremotos de Nueva Zelanda. Esto sugiere, que se requieren longitudes de ruptura y áreas mucho más grandes en América Central con respecto a Nueva Zelanda, para poder provocar sismos de la misma magnitud. Una posible consideración sobre esto es que las rocas de la corteza en Centroamérica podrían presentar un módulo de rigidez (μ), considerablemente más bajo que las de Nueva Zelanda, con lo cual se explicaría en cierta medida el porqué de que los terremotos corticales en América Central no presenten ruptura superficial, ni magnitudes tan grandes con tanta frecuencia como si ocurre en Nueva Zelanda. Finalmente, se proponen nuevas relaciones empíricas para los parámetros de longitud, ancho y área de ruptura. Estas relaciones específicas para América Central son de gran utilidad y un aporte muy importante para su uso en futuros estudios de amenaza sísmica. Las ecuaciones propuestas han sido validadas por medio del mismo análisis de residuales aplicado a las REMT mundiales y se han determinado mejores valores estadísticos del ajuste, con lo cual, finalmente se propone el uso de árboles lógicos que combinan las propuestas para la región y las mundiales. Con base en esto, se sugiere realizar estimaciones de la magnitud utilizando estos árboles lógicos, así como considerar siempre la longitud máxima y segmentada de la falla, un análisis de la sismicidad histórica que ha presentado dicha falla, y diferenciando entre rupturas en profundidad en la zona sismogénica y rupturas en superficie. La selección de REMT para una región específica es un componente particular, pero muy importante en el análisis y cálculos de la amenaza sísmica. La base de datos de terremotos compilada, la recopilación y sugerencia de ecuaciones por implementar, así como las propuestas desarrolladas, contribuyen como un paso muy relevante para la adecuada caracterización de la amenaza y riesgo sísmico en la región.

The triple junction of the North America, Cocos, and Caribbean plates. What we know, what we don’t

Article

Full-text available

Jul 2022

Marco Guzmán-Speziale

We present a summary of the tectonic elements of the North America-Caribbean-Cocos triple junction area. In the vicinity of the triple junction, displacement related to the North America-Caribbean plate boundary takes place along the left-lateral Motagua-Polochic fault system, and convergence between the Cocos and the other two plates occurs along the Middle America trench. The trace of the Motagua-Polochic system is lost at its westernmost end and does not reach the convergent boundary. Deformation of the plate boundary in this location is then distributed along a system of reverse faults (the Reverse-faults tectonic province), a system of left-lateral faults (Strike-slip faults province), two or more large NW-SE oriented left-lateral faults (Angostura and Concordia faults), and a left-lateral fault (Tonalá) that might be construed as the continuation of the Polochic fault along the southern border of the Chiapas Massif. Somewhere within this deformation zone, transition in overriding plate between North America and Caribbean takes place, but it is not clear exactly where. It is probably at about longitude 96° W because both the dip and the shape of the subducted Cocos slab change significantly at this longitude.

Seismicity and seismically active faulting of Guatemala: A review

Article

Feb 2022
J S AM EARTH SCI

We present a review of the main sources of seismicity of Guatemala. The largest seismically active faults are related to the transform, left-lateral, North America-Caribbean plate boundary zone, the most prominent of which are the Motagua and Polochic faults, both exceeding 350 km in length. Additionally, the Ixcán fault, a 150-200-km-long left-lateral structure, is located north of the Polochic and Motagua faults. Other seismically active faults associated to the Polochic-Motagua system and smaller in length are the Seleguá, Nentón and Las Conchas. The Jocotán and Chamelecón faults are located south of and parallel to, the Polochic-Motagua, with a combined length of about 300 km. These faults are not active at present but probably were part of the plate boundary zone in the geologic past. A system of North-South-trending grabens is located immediately south of the Jocotán-Chamelecón fault system, and cutting through it. These grabens are seismically active. South-southwest of the grabens, there is a system of conjugate faults, called the Arco Volcánico fault system, whose main structure is the Jalpatagua fault, a right-lateral strike-slip structure parallel to the volcanic arc. There are other minor faults along this system striking perpendicular to the Jalpatagua with left-lateral displacement. These faults are partially covered by volcanic deposits and have only been identified by their seismic activity. Finally, the Middle America trench offshore southern Guatemala is the plate boundary between the overriding Caribbean and the subducting Cocos plates. All these structures have produced large earthquakes. Historical data show that epicenters of great earthquakes have indeed been located along one of these faults, such as the July 22, 1816 (Magnitude 7.6) along the Polochic fault. More recently, on February 4, 1976, a Magnitude 7.5 earthquake took place, with epicenter on the Motagua fault. This event caused severe damages to the infrastructure of the country, and about 23,000 deaths. The rest of the faults and grabens have also been the site of destructive earthquakes, such as the seismic sequence of December 1917–January 1918, which caused severe damages in Guatemala City. The Cocos-Caribbean convergent boundary is also seismically active, producing events of magnitude 7.0 or larger, the latest of which took place on November 2012, damaging towns and cities along the coastal plain of southern Guatemala.

MARCA-GEHN, a prototype macroseismic archive of four Central America countries MARCA-GEHN, un archivio macrosísmico prototípico para cuatro países de Centroamerica

Article

Full-text available

Mar 2021
B GEOFIS TEOR APPL

In the frame of activities of the RIESCA Project, funded by the Italian Agency for Development Cooperation, the Seismology Working Group (SWG) agreed to build up a prototypal archive of macroseismic data points for the four Central America countries involved in the project, namely, El Salvador, Guatemala, Honduras, and Nicaragua. The objective of this collection is to establish a transnational, common, quality- checked macroseismic archive, for documenting, validating, and eventually updating the earthquake parameters of damaging and destructive events. The new earthquake parameters, supported by documented observations, can be used to update the regional earthquake catalogues and enter into more reliable fault/area source characterisation for seismic hazard purposes. Further, the seismic histories at the site may serve as benchmarks for local response analyses in metropolitan areas. With collaborative efforts, the procedure for selecting and inputting the data into working repositories was defined and realised in 2017: the first data collection adopted basic GoogleTM tools. During 2018, the RIESCA SWG uploaded and updated about 2030 intensity datapoints (IDPs) of some dozens of earthquakes, following codified revision phases. In 2019, we released the first online prototypal archive, named MARCA-GEHN (Macroseismic Archive of Central America - Guatemala, El Salvador, Honduras, Nicaragua, V.1.0), based on the MIDOP (Macroseismic Intensity Data Online Publisher) tools. The present MARCA-GEHN release (V.1.6, September 2020) allows the queries by earthquake and by locality, with interactive maps and seismic histories at more than 1080 sites. We will present the general features of the database and describe the more interesting case studies among the earthquakes collected. MARCA-GEHN is open to collaborative efforts for its further improvement and refinements.

Architectural and Tectonic Control on the Segmentation of the Central American Volcanic Arc

Article

May 2021

Central America has a rich mix of conditions that allow comparisons of different natural experiments in the generation of arc magmas within the relatively short length of the margin. The shape of the volcanic front and this margin's architecture derive from the assemblage of exotic continental and oceanic crustal slivers, and later modification by volcanism and tectonic activity. Active tectonics of the Cocos-Caribbean plate boundary are strongly influenced by oblique subduction, resulting in a narrow volcanic front segmented by right steps occurring at ∼150-km intervals. The largest volcanic centers are located where depths to the slab are ∼90–110 km. Volcanoes that develop above deeper sections of the subducting slab are less voluminous and better record source geochemical heterogeneity. Extreme variations in isotopic and trace element ratios are derived from different components of the subducted oceanic lithosphere. However, the extent that volcanoes sample these signatures is also influenced by lithospheric structures that control the arc segmentation. ▪ The architecture of Central America derives from the assemblage of exotic continental and oceanic crustal slivers modified by arc magmatism and tectonic processes. ▪ Active tectonics in Central America are controlled by oblique subduction. ▪ The lithospheric architecture and tectonics define the segmentation of the volcanic front, and thus the depth to the slab below a volcanic center. ▪ The composition of the subducted material is the main control of the along arc geochemical variations observed in Central American volcanoes. ▪ Geochemical heterogeneity in each segment is highlighted by extreme compositions representing the smaller centers with variations up to 65% of the total observed range. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 49 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Seismicity and active faulting associated with the North America–Caribbean plate boundary in Chiapas, Mexico: A review

Chapter

Aug 2020

This volume furthers our understanding of key basins in central and southern Mexico, and establishes links to exhumed sediment source areas in a plausible paleogeographic framework. Authors present new data and models on the relations between Mexican terranes and the assembly and breakup of western equatorial Pangea, plate-tectonic and terrane reconstructions, uplift and exhumation of source areas, the influence of magmatism on sedimentary systems, and the provenance and delivery of sediment to Mesozoic and Cenozoic basins. Additionally, authors establish relationships between basement regions (sediment source) in the areas that supplied sediment to Mesozoic rift basins, Late Cretaceous foreland systems, and Cenozoic basins developed in response to Cordilleran events.

Base de datos de fallas cuaternarias de México

Article

Full-text available

Apr 2017

We present a Geographic Information System (GIS) database that synthesizes information on the geometry, the sense of movement and the last displacement on known Quaternary faults in Mexico. Faults are classified according to the age of the last known geologic displacement and the quantity and quality of the information available. Class A faults have documented displacement in the Holocene; Class B faults have Pleistocene displacement with possible reactivation in the Holocene; and Class C faults have a last known displacement in the Pleistocene. The database includes the fault name, the type of fault, the fault geometry, the fault length, the evidence for displacement, the slip rate, the recurrence interval, and the size of the most recent earthquake associated with each fault. The database compiles Quaternary fault information for Mexico that can be readily updated as more geologic data become available.

Mexico Quaternary Fault Database

Article

Full-text available

Apr 2017

Luca Ferrari

We present a Geographic Information System (GIS) database that synthesizes information on the geometry, the sense of movement and the last displacement on known Quaternary faults in Mexico. Faults are classified according to the age of the last known geo- logic displacement and the quantity and quality of the information available. Class A faults have documented displacement in the Holocene; Class B faults have Pleistocene displacement with possible reactivation in the Holocene; and Class C faults have a last known displacement in the Pleistocene. The database includes the fault name, the type of fault, the fault geometry, the fault length, the evidence for displacement, the slip rate, the recurrence interval, and the size of the most recent earthquake associated with each fault. The database compiles Quaternary fault information for Mexico that can be readily updated as more geologic data become available.

Caracterización granulométrica de los depósitos de abanicos aluviales en la Cuenca de Motozintla, Chiapas, México: Un peligro geológico latente por eventos de inundación

Article

Full-text available

Jan 2017

Motozintla basin is situated in the southern mountainous region of Chiapas State, Mexico, where debris flows have frequently occurred. These natural phenomena are latent geohazards for the population of Motozintla. Their sudden nature, their high energy, related unstable slopes ( > 30°), rugged topography and anthropogenic footprint contribute to make them more dangerous. This basin is located in the western end of the left lateral Polochic fault - the structural limit of North America and the Caribbean plates. Tectonically, the basin encompasses alluvial fans and terraces that cut both sides of the plate boundary. This study deals with the alluvial fans that are composed of successive deposits, some separated by underdeveloped paleosoils. Granulometric characteristics of 57 deposits sampled in 30 stratigraphic columns were determined. The results revealed that most alluvial fans were sourced from immature flows (lithological, heterometric and various other sources) transported on steep slopes ( > 30°) with less than 10 km of transport from the source. The repeated occurrence of these events in the past indicates that the events of debris flow are influenced by hydrometerological and seismological processes. This research is the first of its kind in an active tectonic setting of Mexico.

Block tectonics in and around the Caribbean: a review

Article

Full-text available

Jan 2014

Franck A. Audemard

Abstract. The knowledge of the Caribbean and its plate boundaries has largely improved along the last 35 years despite getting progressively much more complex. The borders of the Caribbean plate are actual plate boundary zones –PBZ-, in which many tectonic blocks of different size, composition, origin and geometry, are amalgamated. These blocks somehow surround the Caribbean large igneous province or oceanic plateau. The identification of tectonic blocks along the southern Caribbean border happened first, boosted by the fact that the plate boundary was much less conspicuous compared to the others. This was favored to a great extent by the boundary cutting across continental areas. Instead, the northern boundary of the Caribbean plate became a natural laboratory for GPS Geodesy because of the apparent simpler geometry of the PBZ. Surprisingly, GPS networks have not solved all targeted kinematic issues because most of the networks are on small islands, sitting within the deformation zone. Several of these islands in fact exist because the contractional deformation made them crop out, such as Jamaica and Hispaniola. This problem is also common to the Caribbean- Atlantic PBZ. Stable reference points inside the Caribbean Sea, such as San Andrés, Providencia and Aves islands, are needed to resolve the motion between North America and Caribbean plates. From recent GPS results, the inner Caribbean plate appears as a single, almost rigid body, at least under the current 2-3 mm/a resolution of the approach. The Hess Escarpment, which exhibits a nonnegligible seismic activity along its southwestern submarine termination close to Costa Rica, may be slipping in that order. Nevertheless, in the frame of the Neogene Caribbean geodynamic evolution, this submarine feature, which cuts the Caribbean ocean floor into two large pieces, juxtaposes two different Caribbean regions at naked eye. Finally, strain partitioning at different scale is common to all Caribbean plate boundaries. Block indentationextrusion and induced subductions are also common. Keywords: Block Tectonics, Escape, Indentation, Induced Subduction, Buoyancy, Oblique Convergence, Hess, Caribbean Resumen In-Extenso. La comprensión del Caribe y sus bordes de placa en los últimos 35 años ha definitivamente mejorado, a pesar de hacerse progresivamente mucho más complejo. De hecho, las fronteras de la placa Caribe son zonas de borde de placa –ZBP-, en las cuales bloques tectónicos de diverso tamaño, composición, origen y geometría están amalgamados (Figuras 1 y 2). Estos bloques de cierta forma rodean la meseta oceánica del Caribe. El reconocimiento de estos bloques tectónicos ocurrió primero a lo largo de su frontera sur, como consecuencia que el límite de placa era menos sobresaliente. Ello se vio ampliamente favorecido por estar la frontera en áreas continentales (Figuras 1 y 2). Por el contrario, el borde septentrional de la placa Caribe se convirtió en un laboratorio natural de geodesia satelital por GPS, como consecuencia de su aparente simplicidad estructural. Sin embargo, las redes GPS no resolvieron las incógnitas cinemáticas planteadas, dado que las redes están instaladas en pequeñas islas, las cuales están inmersas dentro de la propia zona de deformación (Figuras 1 y 2). Varias de estas islas de hecho existen por los procesos contraccionales que las han elevado fuera del mar, tal como Jamaica y Española. Igual situación se presenta a lo largo del borde de placa entre las placas Caribe y Atlántica. Puntos de referencia estable dentro del mar Caribe, tales como las islas de San Andrés, Providencia y Aves, son necesarios para resolver el movimiento relativo entre las placas Norteamericana y Caribe. El proceso de partición de las deformaciones de distintas escalas es común a las cuatro fronteras de la placa Caribe (Figuras 3 y 4). En América Central, una franja costera, limitada por la trinchera mesoamericana y el arco volcánico activo, escapa hacia el NO, aprovechando el debilitamiento de la corteza continental de la placa Caribe por el volcanismo activo a nivel de la América Central. Igual situación es reportada en la porción norte de las Antillas Menores, donde el antearco de este sector de las Antillas se desplaza hacia el norte relativo al resto del arco volcánico. En el límite de placas Norteamérica-Caribe, la franja más septentrional de la isla Española, limitada entre las fallas Española Norte y Septentrional, al norte y sur respectivamente, se desplaza hacia el oeste con respecto al resto de Española. En el margen sur de la placa Caribe, el bloque de Bonaire, asi como el bloque que contiene las napas Caribe sobrecorridas en el norte de Venezuela (aflorantes en Cordillera de la Costa y serranías del Interior central y oriental), hacen lo propio (Figuras 5 y 9), aunque a tasas de movimiento más lento que en los otros bordes de placa. Por otra parte, la indentación y expulsión de bloques, así como subducciones inducidas, son procesos igualmente frecuentes en los bordes de la placa Caribe. La indentación por altos o relieves submarinos de alta flotabilidad (ej., Carnegie y Cocos), como motor de expulsiones de bloques tectónicos, ha sido invocado para el bloque Norandino y la franja costera de América Central que se extiende entre Costa Rica y Guatemala, respectivamente (Figuras 2 a 5). En otros casos, tales particiones de deformaciones han sido atribuidas a la covergencia oblicua entre la placa subductante y la sobrecorrida, como para el caso del antearco de las Antillas Menores del norte y el bloque septentrional de Española (Figura 8). No obstante, el mejor ejemplo regional de indentación-expulsión lo conforma la colisión y posterior suturación del bloque del Chocó (originalmente perteneciente al Arco de Panamá) contra la fachada occidental suramericana, que induce la expulsión de una gran porción de Suramérica, que se extiende entre el golfo de Guayaquil o graben de Jambelí, en Ecuador, y las Antillas Holandesas de Sotavento, al norte de Venezuela, incluyendo toda Colombia montañosa (Figuras 1, 5 y 9). Este proceso es relativamente joven, probablemente iniciado en el Mioceno superior, con el cierre parcial del canal del Caribe, pero hecho efectivo ya en el Plioceno (5-3 Ma), cuando ocurre el paroxismo tectónico más reciente de la Cordillera Oriental de Colombia y de los Andes de Mérida en Venezuela, al igual que la transcurrencia dextral del sistema que se extiende entre las fallas de Dolores (Ecuador) y Boconó (Venezuela). Parte del retardo en el acoplamiento efectivo del bloque de Chocó contra Suramérica, además de la oblicuidad entre los bloques en confrontación, puede deberse a la baja rigidez del indentor (Arco de Panamá), el cual sufre fuertes deformaciones internas (flexión oroclina y fallamiento sinestral de orientación NO-SE; Figura 6). El choque efectivo del bloque Chocó conlleva a la expulsión de los bloques Norandino, Maracaibo y Bonaire hacia el NNE. La subducción que conlleva a esta colisión está hoy día parcialmente fosilizada entre el bloque Chocó y Suramérica, en asociación al sistema de fallas de Romeral. Esta colisión tiene expresión superficial hasta la latitud de 4° N en Colombia, y se expresa en superficie por el alineamiento ENE-OSO de las fallas de Garrapatas, Río Verde, Ibagué y el cambio de estilo estructural del piedemonte llanero de la Cordillera Oriental de Colombia de transcurrencia dextral al sur al de transpresión dextral al norte, aproximadamente a la latitud de Santa Fé de Bogotá. En profundidad, tal cambio estructural al nivel de la losa de subducción de afinidad caribeña (y fuertemente suturada contra el bloque Chocó al sur del golfo de Urabá), coincide con el desgarre de Caldas, ubicado algo más al norte (5,6° N) que su expresión superficial que llega hasta la latitud de 4° N. Esta losa de subducción ha sido muy bien definida recientemente con base en anomalías de velocidades de ondas P, la cual se hunde hacia el ESE, bajo el bloque triangular de Maracaibo y los Andes de Mérida, hasta profundidades de 700 km, pero no alcanza extenderse más al norte de la falla de Oca-Ancón (Figuras 7, 10 y 11), la cual debe funcionar como su desgarre norte, para separarla de la subducción inducida de las Antillas de Sotavento, a la cual se asocia el cinturón de deformación surcaribeño. A partir de vectores GPS, el bloque Norandino senso stricto puede ser subdividido en hasta 13 bloques tectónicos menores (Figura 12), tal como a fines del Proyecto GEORED del Servicio Geológico Colombiano; pero a fines de modelación de deformación rígida se ha fragmentado de manera conservadora en sólo 3 subbloques (Figura 13). Por su parte, el interior de la placa Caribe parece ser una única unidad rígida, al menos hasta la resolución de los resultados GPS del orden de 2-3 mm/a. El escarpe de Hess, el cual presenta una actividad sísmica no despreciable en su extremidad suroeste (Figuras 14 y 15), parece moverse en ese orden de velocidad. No obstante, en términos de la evolución geodinámica neógena del Caribe, este rasgo mayor submarino que corta en dos el piso oceánico Caribe en dirección NE-SO, yuxtapone dos entidades caribeñas muy dispares a simple vista. Proponemos que este accidente puede haber jugado un rol muy importante en la migración relativa hacia el este de la parte meridional caribeña, la contentiva del LIP o meseta oceánica, en el Mioceno medio y el Mioceno superior. Actualmente, se estaría iniciando una reactivación moderna, igualmente con movimiento predominantemente sinestral con componente subordinada normal; pero esta vez ligada a la subducción del alto de Cocos de alta flotabilidad. Palabras clave: Tectónica de Bloques, Escape, Indentación, Subducción Inducida, Flotabilidad, Convergencia Oblicua, Hess, Caribe.

Western Caribbean Tectonics

Chapter

Feb 2014

D. Fraser Keppie

Despite 50 years of study, the evolution of the western Caribbean Plate region is still debated and there are three possible end-members: (1) Pacific model where the western Caribbean lithosphere is derived from the eastern Pacific and the northern and southern Caribbean Plate boundaries connect directly west to the Middle America Trench at the western Caribbean Plate boundary, (2) In-situ model where the western Caribbean lithosphere is derived from depth and the northern and southern Caribbean Plate boundaries terminate in a broad zone of extension in the western Caribbean Plate, and (3) Pirate model where the western Caribbean lithosphere is derived from the southern and northern margins of North and South America, and the northern and southern Caribbean Plate boundaries have either accommodated convergence themselves, or have curved to the north and south prior to reaching the Middle America Trench. Analysis indicates all models have been important for the evolution of the western Caribbean at different times but the Pirate model may have been dominant during the Cenozoic. The Pirate model resolves the absence of fault connections between the northern and southern boundaries of the Caribbean Plate with the Middle America Trench that are essential for the Pacific model and the > 1,100 km of net strike-slip displacements inferred across the northern and southern Caribbean margins that are unexplained by the in-situ model. In the Pirate model, North and South American material is inferred to have rotated into the trailing edge of the Caribbean Plate across the western Caribbean Plate corners.

Geomorphic analysis of transient landscapes in the Sierra Madre de Chiapas and Maya Mountains (northern Central America): Implications for the North American-Caribbean-Cocos plate boundary

Article

Full-text available

Jan 2016

We use a geomorphic approach in order to unravel the recent evolution of the diffuse triple junction between the North American, Caribbean, and Cocos plates in northern Central America. We intend to characterize and understand the complex tectonic setting that produced an intricate pattern of landscapes using tectonic geomorphology, as well as available geological and geophysical data. We classify regions with specific relief characteristics and highlight uplifted relict landscapes in northern Central America.We also analyze the drainage network from the Sierra Madre de Chiapas and Maya Mountains in order to extract information about potential vertical displacements. Our results suggest that most of the landscapes of the Sierra Madre de Chiapas and Maya Mountains are in a transient stage. Topographic profiles and morphometric maps highlight elevated relict surfaces that are characterized by a low-amplitude relief. The river longitudinal profiles display upper reaches witnessing these relict landscapes. Lower reaches adjust to new base-level conditions and are characterized by multiple knickpoints. These results backed by published GPS and seismotectonic data allow us to refine and extend existing geodynamic models of the triple junction. Relict landscapes are delimited by faults and thus result from a tectonic control. The topography of the Sierra Madre de Chiapas evolved as the result of (1) the inland migration of deformation related to the coupling between the Chiapas Massif and the Cocos forearc sliver and (2) the compression along the northern tip of the Central American volcanic arc. Although most of the shortening between the Cocos forearc sliver and the North American Plate is accommodated within the Sierra de Chiapas and Sierra de los Cuchumatanes, a small part may be still transmitted to the Maya Mountains and the Belize margin through a “rigid” Petén Basin.

Geomorphic analysis of transient landscapes from the Sierra Madre de Chiapas and Maya Mountains (northern Central America): implications for the North American–Caribbean–Cocos plate boundary

Article

Full-text available

Sep 2015

We use a geomorphic approach in order to unravel the recent evolution of the diffuse triple junction between the North American, Caribbean, and Cocos plates in northern Central America. The complex tectonic setting produced an intricate pattern of landscapes that we try to systemize using remote sensing tectonic geomorphology and available geological and geophysical data. We classify regions with specific relief characteristics and highlight uplifted relict landscapes in northern Central America. We also analyze the drainage network from the Sierra Madre de Chiapas and Maya Mountains in order to extract information about potential vertical displacements. Our results suggest that most of the landscapes of the Sierra Madre de Chiapas and Maya Mountains are in transient stage. Topographic profiles and morphometric maps highlight elevated relict surfaces that are characterized by a low amplitude relief. The river longitudinal profiles display upper reaches witnessing these relict landscapes while lower segments characterized by multiple knickpoints, that adjust to new base-level conditions. These results backed by published GPS and seismotectonic data allow us to refine and extend existing geodynamic models of the triple junction. Relict landscapes are delimited by faults and thus result from a tectonic control. The topography of the Sierra Madre de Chiapas evolved as the result of (1) the inland migration of deformation related to the coupling between the Chiapas Massif and the Cocos fore-arc sliver, and (2) the compression along the northern tip of the Central America Volcanic Arc. Although most of the shortening between the Cocos fore-arc sliver and the North American plate is accommodated within the Sierra de Chiapas and Sierra de los Cuchumatanes, a small part may be still transmitted to the Maya Mountains and the Belize margin through a "rigid" Petén basin.

Active block tectonics in and around the Caribbean: A Review

Chapter

Full-text available

Dec 2014

Franck A. Audemard

Caribbean - South American interactions: New data and interpretations The South American Plate has a series of classic tectonic boundaries, which go from the Andean type margin, a subduction convergent boundary for over 9,000 km, to the opposite Atlantic-type margin linked to the divergent boundary with the African Plate, even longer than the previous convergent boundary. However, the interaction of the Caribbean and South American plates is one of the most complex boundaries along the entire South American plate. The geology of this continental margin from the Venezuela Basin in the north up to the foreland basins in the south has an intricate tectonic history, where robust geophysical data are required for its comprehension. The present book “The Northeastern Limit of the South American Plate - Lithospheric Structures from Surface to the Mantle” is filling this gap with an extraordinary amount of data, combining the result of new surveys with re-evaluation of the previous data. It is worth to remark that the continental margin of Venezuela benefitted from the pioneer observations of Alexander von Humboldt between 1799 and 1800, who published the first geological cross section of Venezuela (Humboldt, 1803). His works were the first description of the Andes, where a complicated relationship of metamorphic rocks, ophiolites assemblages, and sedimentary deposits were far from being understood. More than two hundred years later, after many geological surveys and geophysical studies, which led to very different models, distinct tectonic block geometries, and ad-hoc geological and geophysical interpretations, the need for a comprehensive study of the Caribbean continental margin of South America was calling for new research. The geophysical crustal signatures along the plate boundary studied by Michael Schmitz, and Alan Levander, together with numerous co-workers, based on broad band receiver function analyses and active seismic data along specific corridors set the stage for robust crustal thickness changes. Important crustal thinning from onshore toward the present Caribbean margin is explained by the composition of the lower crust. The present knowledge of the Caribbean and its plate boundaries has largely improved in the last years, although as a consequence of the new data, it is progressively getting much more complex. The review of the active block tectonics presented by Franck Audemard is an extraordinary brainstorming on the Caribbean geodynamics that will guide discussion for many years to come. The stacks of terranes accreted to northern South American plate that constitute the metamorphic mountains of north-central Venezuela are systematically analyzed by Franco Urbani. A series of metamorphic belts with distinctive terranes, showing different lithologies and geochronological characteristics, are interpreted as para-autochthonous, split from the South American basement during accretion. The different trends of the striped magnetic anomaly of Caribbean Plate are analyzed by Nuris Orihuela and co-workers. Comparison of striped anomaly signatures from the inner Caribbean with those of the Central Atlantic explains the low spreading velocity associated with the Aves ridge that gives rise to the Caribbean chrons. The analysis of mantle dynamics based on seismic anisotropy performed by Laura T. Piñero-Feliciangeli supports once more the previous hypotheses, which suggest that asthenospheric flow circulation around the edges of South America is parallel to the Caribbean-South America plate boundary. The complicated tectonic history of the Caribbean Plate is analyzed by Maximiliano J. Bezada based on the insights from P-wave seismic tomography. He addressed the robust subduction between the Atlantic oceanic crust and the Caribbean plate, and tackles the proposed subduction of the southern Caribbean under the South American Plate. An initial, shallow, stage of subduction with a dip of ~22º is recognized in the western margin of Venezuela at depths greater than 200 km. The integration of the results of different refraction and reflection seismic projects with the interpretations of deep refraction seismic data done by Jesús Ávila and co-workers, obtained interpolated Moho depth maps of northern part of Venezuela. The crustal structure between Caribbean-South America zone with deep seismic profiles and the excellent crustal sections illuminate different tectonic scenarios for the appraisal of the crust between offshore and onshore. The analysis and identification of crustal structures in the Eastern Caribbean by Antonio Ughi based on the gravity anomalies indicate that the tectonic processes that produce the opening of the Grenada basin are related to the inception of a magmatic arc as a consequence of the Atlantic plate roll back. The study of the easternmost mafic dikes of the Tertiary Falcón Basin performed by Franco Urbani and co-workers shows that intrusion took place after the emplacement of the Lara Nappes. These 26 to 24 Ma old dikes were extensionally controlled and have an intraplate affinity, and their emplacement was probably induced by a slab break-off of the remnant of the proto-Caribbean slab attached to South America. The high grade isolated massif of the Yumare region with its complex assemblage of different rock suites was studied by Franco Urbani and co-workers. The study indicates that the deepest thrusts did cut through Grenvillian continental crust, proto-Caribbean oceanic crust, South American passive margin sediments and Eocene turbidites during their emplacement. A geophysical interpretation of the Venezuelan north central coastal platform performed by Mónica Paolini and co-workers was based on passive seismic data of some recent intracrustal earthquakes, combined with six seismic reflection regional lines. These data, together with gravity and magnetic data, support some first class crustal cross- sections across the Los Roques Trough, Leeward Antilles, the Bonaire and Choroní basins and La Guaira Platform. The structural geological model of the north - central coastal platform of Venezuela constructed by Vanessa Villarroel and Nuris Orihuela gathered extensive 2D seismic reflection data, as well as magnetic and gravity data. Based on these data plus the GPS information they conclude that the San Sebastian – El Pilar Fault System could correspond to a lithospheric boundary between the Caribbean and South American plates. A joint inversion of gravity and magnetic data done by Ricardo Blanco and co-workers produced a tridimensional model of the crustal and lithospheric structure in the interaction zone between the Caribbean and South American plates. The 3D results show an incipient subduction of the Caribbean plate beneath the South American plate dipping 30° from the horizontal down to at least 200-300 km south of the accretionary prism. The review presented by Mauricio A. Bermúdez and co-workers of the existing apatite fission-track thermochronology data and their distribution along the Venezuelan Andes is analyzed within the framework of the Caribbean geodynamics. The discussion of the relationships with the different tectonic blocks, the time of collision, and the beginning of the deformation shows complex asynchronous exhumation patterns controlled by pre-existing inherited structures. The analyses performed by Carlos Reinoza and co-workers of the kinematics of faults in Venezuela based on geodetic measurements show a long history of GPS studies to determine slip rates of plate boundary faults. In spite of the significant results obtained by the GPS through the years, the authors call the attention in the needed national efforts to assess the seismic risks of important faults that could produce earthquakes with magnitudes larger than 7. A series of maps of absolute gravity, Bouguer anomalies and total magnetic field anomaly of Venezuela and adjacent regions were obtained by Nuris Orihuela Guevara and Andreina García from satellite data. The results present a general review of the gravity and total magnetic field anomalies of the major geological structural features of Venezuela, depicting several interesting structural features. The chapter of Santiago Yépez and co-workers integrates geophysical and geological data in the Geodinos GIS, as a tool for interdisciplinary interpretation of future geological and geophysical studies. The importance of this Geo Information System is going to be assessed in the coming years for the evaluation of the complex tectonic settings and different geodynamic scenarios of Venezuela. The closing input of Franco Urbani and Alí Gómez enhanced the contributions of the GEODINOS project to the geological mapping of northern Venezuela. An area close to 25,000 km2 was covered by field work, and selected petrological, geochemical and geochronological studies, some of them of relative importance. The book is accompanied by a DVD with the relevant data of the Geodinos GIS, compiled by Jesús Moncada and co-workers, which also comprises the complete set of contributions. As a final remark it is important emphasizing that this volume contains much new data, new interpretations of previously known features, and new ideas on the tectonic evolution of the Caribbean and South American interaction through time and space. As important as the research that produced new ideas and interpretations, it is significant the gathering in the different chapters of this book of a large volume of data collected through different projects and integrated by the Geodinos initiative. These robust datasets will provide a potential focus for new research and initiatives which may eventually contribute in the future to the comprehension of the complex and challenging geodynamic scenarios of Venezuela. The editors Michael Schmitz, Franck Audemard and Franco Urbani should be congratulated for the preparation of this volume, for the selection of the different authors and the level of excellence obtained in the different contributions. An outstanding feature of the book is the massive authorships of Venezuelan colleagues that evidence the maturity reached by the academic community of geophysicists and geologists granting a solid future for the Earth Sciences research in Venezuela.

Late Cretaceous-Oligocene magmatic record in southern Mexico: The case for a temporal slab window along the evolving Caribbean-North America-Farallon triple boundary

Article

Full-text available

Sep 2014

Continental magmatism in southern Mexico is expected to record the eastward displacement of the Farallon-North America-Caribbean triple junction. However, a trench-transversal belt of magmatism in the central-western Guerrero State does not fit into a regular pattern of arc migration and reorientation following the formation of the WSW-trending Acapulco trench in the Cenozoic. We revised the magmatic pattern of southern Mexico using an updated database and new LA-ICPMS, SHRIMP, and Ar-Ar ages, and geochemical and geologic data for the coastal part of the anomalous Guerrero belt. Our data reveal a persistent magmatic activity between ~75 and 35 Ma, with a changing character at the Paleocene-Eocene boundary (ca. 56 Ma). Late Cretaceous-Paleocene granitoids have an adakitic signature imprinted by stable garnet in the source and show no plagioclase fractionation, indicative of wet and oxidized magmas. Eocene rocks consist of an almost bimodal suite of plutonic bodies covered by a succession of mafic lavas. Granitic plutons show plagioclase fractionation and flat MREE-HREE; gabbros have a tholeiitic character, indicative of dryer and more reduced magmas. They appear later and were emplaced at shallow depth in an extensional sedimentary basin. We interpret the magmatic record of the Guerrero belt as the response to two concurrent processes: (1) a temporal window in the Farallon slab induced by the concurrent subduction along the two non-collinear trench segments of southern Mexico (WNW trending) and of the Chortís block (NNW trending), and (2) a scissor-like transtensional rifting associated to counterclockwise rotation and eastward motion of the Chortís block.

Estudio de la Estabilidad del valor b para regiones sismotectónicas de México

Thesis

Full-text available

Nov 2012

In order to find reliable parameters for the evaluation of the seismic hazard, more precise estimates of the b value of the Gutenberg-Richter law were made for the 19 regions into which Mexico was divided according to the seismotectonic regionalization of Zúñiga et al. (1997). The given values provide much more reliable results because they do not consider temporary variations in this seismic parameter.

Evolución geológica del sureste mexicano, Golfo de México Evolución geológica del sureste mexicano desde el Mesozoico al presente en el contexto regional del Golfo de México

Article

Full-text available

Jan 2007

The geologic evolution of southeastern Mexico is analyzed in the regional context of the Gulf of Mexico, which starts it opening with the fragmentation and spreading of Pangea. The sedimentary record in this depression begins with the deposit of continental red beds during the Late Triassic and Early Jurassic, after which, during the Callovian, sea-waters from the Pacific invaded an extense area; low circulation and high evaporation of these waters allowed the deposition of large volumes of salt in the central part of the basin. From Late Jurassic to Late Cretaceous, carbonate deposition prevailed, changing to clastic at the beginning of the Paleogene, when the Laramide Orogeny formed the folds and faults of the Sierra Madre Oriental. During the rest of the Paleogene clastic sedimentation was deposited in large depocenters generated in the foreland of the Sierra Madre Oriental, and in the southern and southwestern partsof the Golf of Mexico, where the Chiapas Massif produced large volumes of sediments, whereas in the Yucatan Block the deposition of shallow water carbonates continued. In the Middle Miocene, during the Serravalian, compressive stresses resulting from the lateral movement of the Chortis Block and the subduction of the Cocos Plate, against the southern end of the North American Plate, formed the folds and faults of the Chiapas-Reforma-Akal belt over a décollement at the level of the Callovian salt; later, these structures were tilted to the NNW when the salt was mobilized northward. The change of location of this mass of salt caused new depocenters and minibasins, comptrolled by faults with a vergence toward the deepest parts of the Gulf of Mexico, and by regional antithetic faults, which limit the Cuencas del Sureste. The gravitational movement of the Cenozoic deposits, finally caused tectonic inversion in the neogene basins, from which the most evident is the Macuspana Basin.

Seismic moment catalog of large shallow earthquakes, 1900 to 1989

Article

Full-text available

Jun 1992

A worldwide catalog of shallow (depth <70 km) and large (Ms ≥ 7) earthquakes recorded between 1900 and 1989 has been compiled. The catalog is shown to be complete and uniform at the 20-sec surface-wave magnitude Ms ≥ 7.0. The catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec. Using these seismic moments for great and giant earthquakes and a moment-magnitude relationship for smaller events, a seismic moment catalog for large earthquakes from 1900 to 1989 is produced. The seismic moment released at subduction zones during this century constitutes 90% of all the moment released by large, shallow earthquakes on a global basis. The seismic moment released in the largest event that occurred during this century, the 1960 southern Chile earthquake, represents about 30 to 45% of the total moment released from 1900 through 1989. -from Authors

Destructive upper-crustal earthquakes of Central America since 1900

Article

Full-text available

Aug 1993

A catalog has been compiled of 51 destructive upper-crustal earthquakes in Central America since 1900. An event is included if it caused casualties or heavy damage of Modified Mercalli (MM) intensity ≥VII. All events larger than magnitude Ms 5.7 are found to be destructive. The catalog includes estimates of epicentral coordinates, depth, magnitude, and casualties for all events and present MM intensity VII contours for most events. Data in this catalog place severe contraints on the spatial, temporal, and magnitude distribution of destructive upper-crustal earthquakes in Central America. The catalog contains 30 events of Ms≥6. Depths of well-constrained mainshock hypocenters range from 5 to 15km. The most striking feature of the catalog is the spatial alignment along the volcanic front of 23 of the 30 events; volcanic-front earthquake-source mechanisms for such events show east-west tension and are compatible with a model of the volcanic front as a zone of right-lateral strike-slip faulting. -from Authors

Geological current plate motions

Article

Full-text available

Apr 2010

We describe best-fitting angular velocities and MORVEL, a new closure-enforced set of angular velocities for the geologically current motions of 25 tectonic plates that collectively occupy 97 per cent of Earth's surface. Seafloor spreading rates and fault azimuths are used to determine the motions of 19 plates bordered by mid-ocean ridges, including all the major plates. Six smaller plates with little or no connection to the mid-ocean ridges are linked to MORVEL with GPS station velocities and azimuthal data. By design, almost no kinematic information is exchanged between the geologically determined and geodetically constrained subsets of the global circuit-MORVEL thus averages motion over geological intervals for all the major plates. Plate geometry changes relative to NUVEL-1A include the incorporation of Nubia, Lwandle and Somalia plates for the former Africa plate, Capricorn, Australia and Macquarie plates for the former Australia plate, and Sur and South America plates for the former South America plate. MORVEL also includes Amur, Philippine Sea, Sundaland and Yangtze plates, making it more useful than NUVEL-1A for studies of deformation in Asia and the western Pacific. Seafloor spreading rates are estimated over the past 0.78 Myr for intermediate and fast spreading centres and since 3.16 Ma for slow and ultraslow spreading centres. Rates are adjusted downward by 0.6-2.6mmyr-1 to compensate for the several kilometre width of magnetic reversal zones. Nearly all the NUVEL-1A angular velocities differ significantly from the MORVEL angular velocities. The many new data, revised plate geometries, and correction for outward displacement thus significantly modify our knowledge of geologically current plate motions. MORVEL indicates significantly slower 0.78-Myr-average motion across the Nazca-Antarctic and Nazca-Pacific boundaries than does NUVEL-1A, consistent with a progressive slowdown in the eastward component of Nazca plate motion since 3.16 Ma. It also indicates that motions across the Caribbean-North America and Caribbean-South America plate boundaries are twice as fast as given by NUVEL-1A. Summed, least-squares differences between angular velocities estimated from GPS and those for MORVEL, NUVEL-1 and NUVEL-1A are, respectively, 260 per cent larger for NUVEL-1 and 50 per cent larger for NUVEL-1A than for MORVEL, suggesting that MORVEL more accurately describes historically current plate motions. Significant differences between geological and GPS estimates of Nazca plate motion and Arabia-Eurasia and India-Eurasia motion are reduced but not eliminated when using MORVEL instead of NUVEL-1A, possibly indicating that changes have occurred in those plate motions since 3.16 Ma. The MORVEL and GPS estimates of Pacific-North America plate motion in western North America differ by only 2.6 +/- 1.7mmyr-1, ~25 per cent smaller than for NUVEL-1A. The remaining difference for this plate pair, assuming there are no unrecognized systematic errors and no measurable change in Pacific-North America motion over the past 1-3 Myr, indicates deformation of one or more plates in the global circuit. Tests for closure of six three-plate circuits indicate that two, Pacific-Cocos-Nazca and Sur-Nubia-Antarctic, fail closure, with respective linear velocities of non-closure of 14 +/- 5 and 3 +/- 1mmyr-1 (95 per cent confidence limits) at their triple junctions. We conclude that the rigid plate approximation continues to be tremendously useful, but-absent any unrecognized systematic errors-the plates deform measurably, possibly by thermal contraction and wide plate boundaries with deformation rates near or beneath the level of noise in plate kinematic data.

Tectonic Implications of Alternative Cenozoic Reconstructions for Southern Mexico and the Chortis Block

Article

Full-text available

May 2005

Most current Eocene reconstructions juxtapose the Chortis block of northern Central America against southern Mexico, and invoke ˜1100 km Cenozoic sinistral displacement on the Acapulco-Motagua-Cayman fault zone, the inferred northern margin of the Caribbean plate. Such a hypothesis is incompatible with the presence of undeformed Upper Cretaceous—Recent sediments that cross the projected trace of the Motagua fault zone in the Gulf of Tehuantepec, minimal offset of the Permian Chiapas batholith, and the absence in Honduras of several major features in southern Mexico. These problems may be overcome if the Chortis block is back-rotated anticlockwise about a pole near Santiago, Chile, i.e. ˜1100 km along the Cayman transform faults during the Cenozoic. Such a reconstruction when combined with reconstructions of features in the Pacific Ocean, suggests that Middle Miocene collision of the Tehuantepec aseismic ridge with the Acapulco Trench led to: (1) asymmetric flattening of the subduction zone; (2) an anticlockwise rotation of the Mexican magmatic arc to its present location by the Middle Miocene; (3) the development of a volcanic arc gap in southeastern Mexico, in which the late Middle Miocene Chiapas fold-and-thrust belt developed: as the Tehuantepec Ridge swept westward, arc volcanism was re-established in the gap. Eocene collision of the Chumbia Seamount Ridge (inferred mirror image of the Moonless Mountains—unnamed seamount ridge between the Molokai and Clarion fracture zones) with the Acapulco Trench followed by its ESE migration during the Oligocene led to: (a) flattening of the subducting slab inducing subduction erosion and exhumation of the southern Mexican margin; (b) anticlockwise rotation of the volcanic arc; and (c) sinistral strike-slip faulting in the Sierra Madre del Sur. This contrasts with the region north of the projected Molokai fracture zone where the dip of the subduction zone appears to have steepened, producing extension. Eocene(—Late Cretaceous) subduction along the southern coast of Mexico explains the remnants of a Late Cretaceous arc in the Gulf of Tehuantepec and neighboring Guatemala.

Permo-Triassic Reconstruction of Western Pangea and the Evolution of the Gulf of Mexico/caribbean Region

Article

Full-text available

Apr 1982

A Permo-Triassic reconstruction of western Pangea (North America, South America, Africa) is proposed that is characterized by (1) definition of the North Atlantic fit by matching of marginal offsets (fracture zones) along the opposing margins, (2) a South Atlantic fit that is tighter than the BuIlard fit and that is achieved by treating Africa as two plates astride the Benue Trough and related structures during the Cretaceous, (3) complete closure of the Proto-Atlantic Ocean between North and South America, accomplished by placing the Yucatan block between the Ouachita Mountains and Venezuela, (4) a proposed Hercynian suture zone that separates zones of foreland thrusting from zones of arc-related magmatic activity; to the northwest of this suture lie the Chortis block and Mexico and most of North America, and to the southeast lie South America, the Yucatan Block, Florida and Africa, and (5) satisfaction of paleomagmatic data from North America, South America, and Africa. Beginning with the proposed reconstruction, the relative motion history of South America with respect of North America is defined by using the finite difference method. Within the framework provided by the proposed relative motion history, an evolutionary model for the development of the Gulf of Mexico and Caribbean region is outlined in a series of 13 plate boundary reconstructions at time intervals from the Jurassic to the present. The model includes (1) formation of the Gulf of Mexico by 140 Ma, (2) Pacific provenance of the Caribbean plate through the North America-South America gap during Cretaceous time, (3) Paleocene-Early Eocene back arc spreading origin for the Yucatan Basin, whereby Cuba is the frontal arc and the Nicaragua Rise-Jamaica-Southern Hispaniola is the remnant arc, and (4) 1200 km of post-Eocene cumulative offset along both the Northern and Southern Caribbean Plate Boundary Zones, allowing large-scale eastward migration of the Caribbean plate with respect to the North and South American Plates.

Quaternary faulting along the Caribbean-North America plate boundary in Central America

Article

Full-text available

Feb 1979
TECTONOPHYSICS

Recent detailed mapping along the Motagua fault zone and reconnaissance along the Chixoy—Polochic and Jocotán—Chamelecón fault zones provide new information regarding the nature of Quaternary deformation along the Caribbean—North American plate boundary in Central America.The southern boundary of the Motagua fault zone is defined by a major active left-slip fault that ruptured during the February 4, 1976 Guatemala earthquake. The recurrent nature of slip along the fault is dramatically demonstrated where stream terraces of the Río El Tambor show progressive left-slip and vertical (up-to-the-north) slip. Left-slip increases from 23.7 m (youngest mappable terrace) to 58.3 m (oldest mappable terrace) and vertical slip increases from 0.6 m to 2.5 m. The oldest mappable terrace crossed by the fault appears to be younger than 40,000 years and older than 10,000 years.Reconnaissance along the Chixoy—Polochic fault zone between Chiantla and Lago de Izabal has located the traces of a previously unmapped major active left-slip fault. Geomorphic features along this fault are similar to those observed along the active trace of the Motagua fault zone. Consistent and significant features suggestive of left-slip have so far not been observed along the Guatemala section of the Jocotán—Chamelecón fault zone.In Central America, the active Caribbean—North American plate boundary is comprised of the Motagua, Chixoy—Polochic, and probably the Jocotán—Chamelecón fault zones, with each accommodating part of the slip produced at the mid-Cayman spreading center. Similarities in geomorphic expression, apparent amount of left-slip, and frequency and magnitude of historical and instrumentally recorded earthquakes between the active traces of the Motagua and Chixoy—Polochic fault zones suggest a comparable degree of activity during Quaternary time; the sense and amount of Quaternary slip on the Jocotán—Chamelecón fault zone remain uncertain, although it appears to be an active earthquake source. Uplift of major mountain ranges on the north side of each fault zone reflects the small but consistent up-to-the-north vertical component (up to 5% of the lateral component) of slip along the plate boundary. Preliminary findings, based on offset stream terraces, indicate a late Quaternary slip rate along the Caribbean—North American plate boundary of between 0.45 and 1.8 cm/yr. Age dating of offset Quaternary terraces in Guatemala will allow refinement of this rate.

The Triple Junction of the North America, Cocos, and Caribbean Plates: Seismicity and tectonics

Article

Full-text available

Oct 1989

The triple junction of the North America, Cocos, and Caribbean plates is ambiguously defined, mainly because the North America-Caribbean plate boundary does not clearly continue beyond its known surface trace (the Motagua fault zone) in western Guatemala to intersect the Middle America trench. Well-located regional shallow earthquakes (h≤70 km) show that there is no intermediate or large-magnitude seismic activity associated with a presumed extension of the North America-Caribbean plate boundary to the west, beyond its well-defined surface trace. There is, however, a clear zone of shallow seismic activity from the western section of the fault system through southern Mexico. Fault plane solutions for these events indicate a left-lateral strike-slip displacement, which is in good agreement with surface faulting. We suggest that these strike-slip faults, together with the Salina Cruz fault in the isthmus of Tehuantepec, mark the boundaries of a broad zone of deformation in southern Mexico and northern central America which takes up the interactions of the three plates. In this sense, no single point constitutes the triple junction. The geologic record suggests that the Motagua fault zone developed because the westernmost portion of the Caribbean plate became locked against North America.

Relative motion between the Caribbean and North American plates and related boundary deformation from a decade of GPS observations

Article

Full-text available

Jul 1998

Global Positioning System (GPS) measurements in 1986, 1994, and 1995 at sites in Dominican Republic, Puerto Rico, Cuba, and Grand Turk define the velocity of the Caribbean plate relative to North America. The data show eastward motion of the Caribbean plate at a rate of 21+/-1mm/yr (1 standard error) in the vicinity of southern Dominican Republic, a factor of 2 higher than the NUVEL-1A plate motion model prediction of 11+/-3mm/yr. Independent measurements on San Andres Island, and an Euler vector derived from these data, also suggest a rate that is much higher than the NUVEL-1A model. Available data, combined with simple elastic strain models, give the following slip rate estimates for major left-lateral faults in Hispaniola: (1) the North Hispaniola fault offshore the north coast of Hispaniola, 4+/-3mm/yr; (2) the Septentrional fault in northern Dominican Republic, 8+/-3mm/yr; and (3) the Enriquillo fault in southern Dominican Republic and Haiti, 8+/-4mmyr. The relatively high plate motion rate and fault slip rates suggested by our study, combined with evidence for strain accumulation and historical seismicity, imply that seismic risk in the region may be higher than previous estimates based on low plate rate/low fault slip rate models and the relatively low rate of seismicity over the last century.

U-Pb zircon geochronology of Paleozoic units in Western and Central Guatemala: Insights into the tectonic evolution of Middle America

Article

Full-text available

Dec 2009

Precambrian and Paleozoic basements are present in southern Mexico and Central America, where several crustal blocks are recognized by their different geologic record, and juxtaposed along lateral faults. Some of those crustal blocks are currently located between southernmost north America (the Maya block) and Central America (Chortis block).To better understand the geology of these crustal blocks, and to establish comparisons between their geologic history, U-Pb ages of both igneous and metasedimentary key units cropping out in central and western Guatemala are presented here. In the Altos Cuchumatanes (Maya block) granites yield both Permian (269 +/- 29 Ma) and Early Devonian (391 +/- 7.4 Ma) U-Pb ages. LA-ICPMS detrital zircon ages from rocks of the San Gabriel sequence, interpreted as the oldest metasedimentary unit of the Maya block, and overlain by the Late Paleozoic Upper Santa Rosa Group, yield Precambrian detrital zircons bracketed between 920 Ma and 1,000 Ma. The presence of these metasedimentary units, as well as Early Devonian to Silurian granites in the Mayan continental margin, from west (Altos Cuchumatanes), to east (Maya Mountains of Belize) indicate a more or less continuous belt of Lower Paleozoic igneous activity, also suggesting that the continental margin of the Maya block can be extended south of the Polochic fault, up to the Baja Verapaz shear zone. A metasedimentary sample belonging to the Chuacus Complex yielded detrital zircons with ages between 440 Ma and 1,325 Ma. The younger ages are similar to the igneous ages reported from the entire southern Maya continental margin, and show proximity of the Complex in the Middle-Late Palaeozoic. The S. Diego Phyllite, which overlies high-grade basement units of the Chortis block, contains zircons that are Lower Cambrian (538 Ma), Mesoproterozoic (980 to 1,150 Ma) and even Paleoproterozoic (1,820 Ma). Absence of younger igneous zircons in the San Diego Phyllite indicates that either its sedimentation took place in a close range of time, during the Late Cambrian, or absence of connection between Chortis and Maya blocks during the Early-Mid Palaeozoic. The Precambrian zircons could have come from southern Mexico (Oaxaca and Guichicovi Complexes), or from Mesoprterozoic Massifs exposed in Laurentia and Gondwana. Paleogeographic models for Middle America are limited to post-Jurassic time. The data presented here shed light on Paleozoic and, possibly, Precambrian relationships. They indicate that Maya and the Chortis did not interact directly until the Mesozoic or Cenozoic, as they approached their current position.

Current Plate Motions

Article

Full-text available

May 1990
GEOPHYS J INT

Best-fitting Euler vectors, closure-fitting Euler vectors, and a new global model (NUVEL-1) describing the geologically current motion between 12 assumed-rigid plates, were determined. The 1122 data from 22 plate boundaries inverted to obtain NUVEL-1 consist of 277 spreading rates, 121 transform fault azimuths, and 724 earthquake slip vectors. The model fits the data well. The strikes of transform faults mapped with GLORIA and Seabeam along the Mid-Atlantic Ridge greatly improve the accuracy of estimates of the direction of plate motion. Data shows that motion about the Azores triple junction is consistent with plate circuit closure, and better resolves motion between North America and South America. Motion of the Caribbean plate relative to North or South America is about 7 mm yr-1 slower than in prior global models. The direction of slip in trench earthquakes tends to be between the direction of plate motion and the normal to the trench strike. -from Authors

Intra-arc extension in Central America: Links between plate motions, tectonics, volcanism, and geochemistry

Article

Full-text available

Jul 2008
EARTH PLANET SC LETT

This study revisits the kinematics and tectonics of Central America subduction, synthesizing observations of marine bathymetry, high-resolution land topography, current plate motions, and the recent seismotectonic and magmatic history in this region. The inferred tectonic history implies that the Guatemala–El Salvador and Nicaraguan segments of this volcanic arc have been a region of significant arc tectonic extension; extension arising from the interplay between subduction roll-back of the Cocos Plate and the ~ 10–15mm/yr slower westward drift of the Caribbean plate relative to the North American Plate. The ages of belts of magmatic rocks paralleling both sides of the current Nicaraguan arc are consistent with long-term arc-normal extension in Nicaragua at the rate of ~ 5–10mm/yr, in agreement with rates predicted by plate kinematics. Significant arc-normal extension can ‘hide’ a very large intrusive arc-magma flux; we suggest that Nicaragua is, in fact, the most magmatically robust section of the Central American arc, and that the volume of intrusive volcanism here has been previously greatly underestimated. Yet, this flux is hidden by the persistent extension and sediment infill of the rifting basin in which the current arc sits. Observed geochemical differences between the Nicaraguan arc and its neighbors which suggest that Nicaragua has a higher rate of arc-magmatism are consistent with this interpretation. Smaller-amplitude, but similar systematic geochemical correlations between arc-chemistry and arc-extension in Guatemala show the same pattern as the even larger variations between the Nicaragua arc and its neighbors.

Global teleseismic earthquake relocation with improved travel times and procedures for depth relocation

Article

Full-text available

Jun 1998

Free software helps map and display data

Article

Full-text available

Jan 1991
Eos Trans. AGU

When creating camera‐ready figures, most scientists are familiar with the sequence of raw data → processing → final illustration and with the spending of large sums of money to finalize papers for submission to scientific journals, prepare proposals, and create overheads and slides for various presentations. This process can be tedious and is often done manually, since available commercial or in‐house software usually can do only part of the job. To expedite this process, we introduce the Generic Mapping Tools (GMT), which is a free, public domain software package that can be used to manipulate columns of tabular data, time series, and gridded data sets and to display these data in a variety of forms ranging from simple x‐y plots to maps and color, perspective, and shaded‐relief illustrations. GMT uses the PostScript page description language, which can create arbitrarily complex images in gray tones or 24‐bit true color by superimposing multiple plot files. Line drawings, bitmapped images, and text can be easily combined in one illustration. PostScript plot files are device‐independent, meaning the same file can be printed at 300 dots per inch (dpi) on an ordinary laserwriter or at 2470 dpi on a phototypesetter when ultimate quality is needed. GMT software is written as a set of UNIX tools and is totally self contained and fully documented. The system is offered free of charge to federal agencies and nonprofit educational organizations worldwide and is distributed over the computer network Internet.

Constraints from finite element modeling on the active tectonics of northern Central America and the Middle America Trench

Article

Full-text available

Feb 2008

We have developed an elastic finite element model in order to study the role of the different forces acting on the northwestern part of the Central American Volcanic Arc and the Chortis Block. We present synthetic focal mechanisms, maps of tectonic regime, and strain crosses to analyze the results. The models show that to achieve the observed state of stress on the volcanic arc, the arc must be modeled as a lithospheric weak zone. Also, the forces related to the eastward drift of the Caribbean plate must be higher than those related to the subduction of the Cocos plate. The coupling on the subduction interface must be low, with or without slip-partitioning due to the obliquity of the subduction at the trench. At Guatemala the western edge of the Chortis block is pinned against North America, even with low trench-normal forces, making the triple junction between the Cocos, North American, and Caribbean plates a zone of diffuse deformation. The extension in the western part of the Chortis block, from Guatemala to the Honduras depression, is explained by the geometry of the North American-Caribbean plate boundary and the direction of motion of the Caribbean plate with respect to North America. The direction of extension in the Chortis block is always E-W regardless of the magnitude of the applied forces, and the main part of the deformation is absorbed between the Ipala graben and the Honduras depression, both features being consistent with our models.

A test of alternative Caribbean Plate relative motion models

Article

Full-text available

May 1988

The new NUVEL-1 data set for global relative plate motions is used here to discriminate between the two prevailing models for Caribbean plate motion. One model, by Jordan (1975), assumes that North America-Caribbean motion is reflected by the spreading rate inferred from magnetic anomalies at the Cayman Spreading Center and the azimuths of nearby transforms. The other model, by Sykes et al. (1982), uses rates and azimuths inferred from the geometry of the Lesser Antilles Wadati-Benioff zone. Overall, it is found that the data fit the Jordan geometry better, that the data used in global plate motion models are more suitable than rates and azimuths inferred from the geometry of the Wadati-Benioff zone for determining relative motions, and that incorporation of all relevant plate boundaries is essential.

Paleogeografía del Paleozoico de Chiapas, México

Article

Jan 1973

R. Hernández-García

Overview of plate tectonic history and its unresolved tectonic problems

Article

Jan 2007

Structural development of northern Central America

Article

Jan 1969

Catalog of historic seismicity in the vicinity of the Chixoy-Polochic and Motagua Faults

Article

Jan 1984

Randall White

Tectonic evolution of the Ixtapa graben, an example of a stake-slip basin of southeastern Mexico: Implications for regional petroleum systems

Article

Jan 2001

Javier Rocha

The Ixtapa graben is located in the center of the Strike-slip Fault province of the Sierra de Chiapas, Mexico. In this graben, rocks of middle Cretaceous (Albian-Cenomanian) to Pleistocene age represent a section in which successively younger beds lie to the southeast. This section is 15,365 m thick and represents marine, transitional, and continental environments with numerous vertical and lateral facies changes through the whole section and unconformities in the uppermost part. Along the flanks of the graben, beds are upturned and form positive flower structures.

Tectonic evolution of the Strike-slip Fault province of Chiapas

Article

Jan 1985

Javier Rocha

Geología petrolera de la Sierra de Chiapas

Article

Jan 1979

R. Sanchez-Montes De Oca

The Guatemala earthquake of 1816 on the Chixoy-Polochic fault

Article

Jan 1985

Randall White

Forty historical documents have been found which describe a previously unknown very large earthquake on 22 July 1816. This event occurred along the strike-slip boundary between the Caribbean and North American plates in Gua-temala and southern Mexico. Modified Mercalli intensities are estimated from these accounts, and a rough isoseismal map is constructed. The damage pattern indicates that the causative fault was the left-lateral Chixoy-Polochic fault for which no damaging earthquake has previously been reported. Damage of Modi-fied Mercalli intensity VII or greater covered an area of at least 13,000 km 2, extending over 340 km from Alta Verapaz province in Guatemala westward to San Cristobal las Casas, in Chiapas, Mexico. The area of intensity VII indicates a moment of 1 x 1028 dyne-cm, while the estimated length of the intensity VII isoseismal indicates a more likely figure of 3.5 x 1027 dyne-cm, or an equivalent magnitude (Mw) of 7~ to 7~. The reported aftershock sequence is compatible with an earthquake in this magnitude range. These data demonstrate that the Chixoy-Polochic fault is currently an active part of the Caribbean-North American plate boundary and is capable of producing very large earthquakes.

The southern Mexico block: Main boundaries and new estimation for its Quaternary motion

Article

Mar 2008

Numerous studies, mainly based on structural and paleomagnetic data, consider southern Mexico as a crustal block (southern Mexico block, SMB) uncoupled from the North American plate with a southeast motion with respect to North America, accommodated by extension through the central Trans-Mexican volcanic belt (TMVB). On the other hand, the accommodation of this motion on the southeastward boundary, especially at the Cocos–Caribbean–North American triple junction, is still debated. The boundary between the SMB and the North American plate is constituted by three connected zones of deformation: (1) left-lateral transtension across the central TMVB, (2) left-lateral strike-slip faulting along the eastern TMVB and Veracruz area and (3) reverse and left-lateral strike-slip faulting in the Chiapas area. We show that these three active deformation zones accommodate a counterclockwise rotation of the SMB with respect to the North American plate. We specially discuss the Quaternary motion of the SMB with respect to the surrounding plates near the Cocos–Caribbean–North American triple junction. The model we propose predicts a Quaternary counterclockwise rotation of 0.45°/Ma with a pole located at 24.2°N and 91.8°W. Finally we discuss the geodynamic implications of this counterclockwise rotation. The southern Mexico block motion is generally assumed to be the result of slip partitioning at the trench. However the obliquity of the subduction is too small to explain slip partitioning. The motion could be facilitated by the high thermal gradient and gravitational collapse that affects central Mexico and/or by partial coupling with the eastward motion of the Caribbean plate.

The North America-Caribbean plate boundary west of the Motagua-Polochic fault system: A fault jog in Southeastern Mexico

Article

Oct 2000
J S AM EARTH SCI

We propose a model for the western end of the North American-Caribbean plate boundary. We suggest that, beyond the surface trace of the Motagua-Polochic fault system, interplate strain is distributed along the Reverse Faults Tectonic Province, a zone of long, narrow anticlines cut along their flanks by reverse faults that generally eliminate the intervening synclines, and the strike-slip faults of southeastern Mexico, a system of at least nine major faults with left-lateral displacement and documented seismic activity. The reverse faults act as a stepover (fault jog) between the strike-slip faults and the Motagua-Polochic system. Comparison with available stress data and models of the stress field at a stepover agree well with the observed pattern of folding and faulting in the area. Proposed displacement and seismicity along each individual fault in the SE Mexico strike-slip system must be small because interplate strain is shared between at least seven major strike-slip faults. We suggest that motion between North America and the Caribbean dies out at the northwestern end of the strike-slip faults.

Motion of Caribbean Plate during last 7 million years and implications for earlier Cenozoic movements

Article

Dec 1982

The direction and rate of movement of the Caribbean plate with respect to North America are determined from the slip vectors of shallow earthquakes and from the configuration of downgoing seismic zones in the Greater and Lesser Antilles. A calibration of the relative plate motion for the NE Caribbean using data from other subduction zones indicates an average rate of 3.7+ or -0.5cm/yr from the past 7Ma. The direction of plate motion inferred from focal mechanisms (ENE) is nearly the same as that deduced from the configuration of downgoing seismic zones going around the major bend in the arc. With respect to North America, the Caribbean plate is moving at an angular velocity of 0.36o/Ma about a center of rotation near 66oN, 132oW. Vector addition using those data and that for the relative motion of N and S America indicates that the Caribbean is moving at an angular velocity of 0.47o/Ma about a center of rotation near 60oN, 88oW with respect to South America. At least three fragments of anomalous seafloor have been sutured onto Hispaniola in the past 50Ma. -Authors

The present-day motions of the Caribbean Plate

Article

Nov 1975

Thomas Jordan

Data pertaining to the instantaneous relative motions of the Caribbean plate with respect to the North American and Cocos plates have been inverted by using the iterative fitting algorithm formulated by Minster et al. (1974). The best-fitting Caribbean-North American pole is located at 50°N+/-18°, 116°E+/-9°, and the computed angular rate is 0.20°+/-0.07°/m.y., which corresponds to a spreading rate of 2.1 cm/yr across the mid-Cayman rise. The model predicts that the present-day motion of South America with respect to the Caribbean is northwestward and suggests that since the late Tertiary this motion has been accommodated along an en echelon series of northwest-trending right lateral strike-slip faults and northeast-trending thrust faults which occupy a broad zone of deformation extending from the Curacao Ridge and its westward extension into the South Caribbean Basin to the frontal thrusts along the southern boundary of the Venezuelan Coast Ranges. The model predicts that the relative motion between the Caribbean and Nazca plates is parallel to the continental margin south of the Gulf of Panama. The rate of motion of the Caribbean plate with respect to the mesosphere, deduced from the fixed hot spot hypothesis, is very small, and this plate may in fact be stationary over the mantle.

41 Global seismicity: 1900–1999

Article

Dec 2002

Seismicity data spanning long periods of time are essential for a thorough understanding of earthquake phenomena. Seismic activity is nonuniform over time and the rate of seismic moment release exhibits large temporal variations. This chapter presents a comprehensive and self-consistent catalog of global seismicity spanning the 20th century. It focuses to produce a comprehensive digital hypocenter and phase arrival-time database for most globally detected earthquakes during the 20th century, including a complete station list with codes, locations, and dates of operation. For the earthquake research community, this database provides a reliable starting point for a wide range of studies—including source parameter studies, delineation of rupture zones of large earthquakes from aftershock distributions, further improvements in Earth models, and detailed studies of the seismicity of active regions. The new database can also be of great utility in providing fundamental information for reliable seismic hazard assessment, especially in developing countries located in active seismic belts whose seismic history is poorly known.

Geology of the Western Altos Cuchumatanes, Northwestern Guatemala

Article

Jan 1973

The western Altos Cuchumatanes is a deeply dissected, northwest-trending, fault-bounded uplift in northwestern Guatemala. About 7,500 m of sedimentary rocks, which is perhaps the thickest exposed section of sedimentary rocks in Central America, lie upon basement rocks consisting of slate, schist, quartzite, gneiss, amphibolite, and intrusive and volcanic rocks of unknown age and thickness. The lowermost overlying strata, consisting predominantly of clastic rocks, are included within the Santa Rosa Group which is composed of the Chicol (800 to 1,200 m), Tactic (800 m), Esperanza (300 to 500 m), and Chóchal (300 to 1,000 m) Formations. The Tactic and Esperanza are probably of Late Pennsylvanian(?) to Permian age, whereas the age of the Chicol, which is probably lithostratigraphically equivalent to the Sacapulas Formation to the east, can only be said to lie within the Ordovician-Permian interval. The Chóchal Formation, composed of fossiliferous limestone and dolomite, locally includes an upper sequence of fine-grained siliciclastic beds intercalated with abundantly fossiliferous carbonate layers, informally known as the Tuilán member. The age of the Chóchal ranges from Leonardian to early Guadalupian. The unconformably overlying Todos Santos Formation is comprised of conglomerate, sandstone, siltstone, shale, and locally contains limestone lenses near the top. Its thickness ranges from a few meters to about 1,200 m, and its age is considered to be Late Jurassic-Early Cretaceous. The Ixcoy Formation, of Cretaceous age, consists of about 2,500 m of carbonate rocks with a few interbeds of fine siliceous clastic material. The Sepur Formation is composed of 245 m of fine-grained red beds, marl, and calcarenite of Campanian to Maestrichtian age. The Colotenango beds (an informal name applied to a lithologic unit confined to the Selegua and Cuilco Valleys) consist of about 500 m of conglomerate, sandstone, mudstone, and volcanic rocks. These beds are probably of late Tertiary and Quaternary age. The youngest sediments in the western Altos Cuchumatanes are Quaternary deposits of till, volcanic ash, and alluvium. Plutonic rocks range in age from early Paleozoic (or older) to Late Cretaceous-early Tertiary. In western Guatemala, and within the western Altos Cuchumatanes, the Chixoy-Polochic fault zone separates pre-Permian crystalline rocks to the south from younger sedimentary rocks to the north. The regional tectonic grain, which is parallel to the Chixoy-Polochic and Motagua fault zones to the east, swings northwestward near Huehuetenango and continues into Mexico where it coincides with regional trends in Chiapas, Mexico. Several probably strike-slip faults splay to the west-northwest, away from the Chixoy-Polochic fault zone. This divergent regional grain is also characterized by broad folds and high-angle normal and reverse faults. Structural relief on the Todos Santos-Ixcoy contact is more than 1,500 m. The age of the latest folding is early Eocene or younger. Two, and possibly more, older episodes of tectonism are evident in the western Altos Cuchumatanes. Intensely folded rocks belonging to the Santa Rosa Group, intruded by late Paleozoic plutons, represent a late Paleozoic mountain structure that lies buried beneath Mesozoic rocks. This buried erosioral high, the Poxlac uplift, was apparently completely covered by the Todos Santos Formation.

Circum-Caribbean Tectonic and Igneous Activity and the Evolution of the Caribbean Plate: Reply

Article

Jan 1973

Convergence of the North and South American blocks and northeastward movement of the East Pacific-Caribbean plate during the Late Cretaceous and early Tertiary led to the Laramide tectonic and igneous activity that has been recorded in the geology of the circum-Caribbean region. Volcanism in Central America and the initiation of major transcurrent faulting along northern South America during the late Eocene suggest that the Caribbean decoupled from the East Pacific plate near the end of the Laramide Orogeny. Lack of post-Eocene structural activity in the Greater Antilles is consistent with the initiation of eastward movement of the Caribbean plate during the Eocene. The evolution of the Cayman Trough and the history of orogenic activity in Cuba can be explained by assuming that Caribbean lithosphere was transferred to the Americas plate as the trough developed from west to east. As each new section was added to the eastward-growing trough, a new transform fault formed in the Caribbean lithosphere to connect the eastern end of the trough with the Cuban Trench. This west to east stepping of the plate boundary transferred "Caribbean" lithosphere to the Americas plate and allowed underthrusting and related tectonic activity to continue longer in eastern than in western Cuba. The presence of intermediate depth earthquakes and high seismicity along the Puerto Rico Trench suggest that the Atlantic lithosphere which underthrust Puerto Rico prior to the Oligocene is beginning to break away from the Americas plate. Fault displacements inferred along the Caribbean-Americas boundary in the Greater Antilles are equivalent to a constant post-Eocene eastward movement of 0.5 cm/yr for the Caribbean plate.

Offset across the Polochic fault of Guatemala and Chiapas, Mexico

Article

Jan 1978
GEOLOGY

Burke Burkart

Polochic fault is seen on LANDSAT imagery to continue its westward path from northwestern Guatemala across the Chiapas massif to the Pacific coastal plain. The fault has had 132 ± 5 km of left-lateral displacement that is recorded in the offset of Cenozoic fold and thrust belt structure and stratigraphy. The trace of the Polochic fault has been folded into what approximates a sinusoidal curve of about 130-km wave length and 7-km amplitude by an essentially east-west compressive stress. The curious similarity in displacement and fold wavelength results in a premovement reconstruction that reveals not only a match across the fault in geology, but an almost perfect fit of one block against the others. Some segments of the fault across which recorded slip took place are probably locked and not active. Strain has shifted to other shears in western Guatemala and Chiapas and to the Motagua fault. Parts of the Polochic and the newer shears may be alternating with the Motagua as the Caribbean-North American plate boundary. With the 132 km of slip removed, segments of the now fragmented Cenozoic fold belt can be brought into coincidence in a clear-cut arcuate trend that is convex southwest. The major fault displacement is believed to have occurred within the interval from middle Miocene to middle Pliocene time. Eastern Guatemala has undergone a counterclockwise rotation of about 25° that reoriented the fault trace and all other structural fabric from due east to the present east-northeast azimuth.

Tectonic Wedges and Offset Laramide Structures Along the Polochic Fault of Guatemala and Chiapas, Mexico: Reaffirmation of Large Neogene Displacement

Article

Aug 1987

Fault wedges along the Polochic fault of northern Guatemala and Chiapas, Mexico record left-lateral slip of from 20 to 65 km that accompanied documented Neogene slip of 130 km across this North American—Caribbean plate boundary fault. Wedges can be correlated to source areas consistent with left-lateral displacement along the Polochic fault. They occur adjacent to restraining bends in three areas where changes in strike of the fault have been mapped. These wedges, which have been previously interpreted as allochthons emplaced along low-angle reverse faults, are bounded by high-angle faults. Folds that terminate against the Polochic fault are part of a regional fold belt that originated during the Campanian through Paleocene (Laramide) orogenic event. A previous contention that some of these major folds are secondary and related to fault movement is shown to be incorrect. The 130 km model of left-lateral offset across the Polochic fault is reviewed along with evidence for and against a Neogene time of major displacement. Additional evidence for the model is presented: (1) Late Cretaceous granitoid rocks from near Motozintla, Chiapas, Mexico (northern fault block), are correlated with granitic rocks of the Santa Maria Batholith in the region of Huehuetenango, Guatemala (southern block), (2) mineralization at the contacts of the granitoid intrusives of the two areas is correlated, (3) points of deflection of Laramide structural axes are correlated across the fault, (4) a major thrust sheet similar to that of the Sierra de Santa Cruz in eastern Guatemala is reassembled by reversing 130 km of left-lateral slip which has offset serpentinites north of the fault in western Guatemala and those south of the fault in central Guatemala.

Seismological Aspects of the Guatemala Earthquake of February 4, 1976

Article

Jul 1978

Detailed analyses of teleseismic surface waves and body waves from the Guatemala earthquake of February 4, 1976, show the following: (1) Left lateral displacement along a vertical fault with a strike varying from N66°E to N98°E is consistent with the teleseismic data. (2) The seismic moment was 2.6×1027 dyn cm. The directivity of the surface wave radiation indicates an asymmetric (1:2.3) bilateral faulting with a total length of 250 km. In modeling the displacement a rupture velocity of 3 km/s was used, and the fault curvature was included. (3) If a fault width of 15 km is assumed, the average offset is estimated to be about 2 m. This value is about twice as large as the average surface offset. (4) Although the observed directivity suggests a uniform overall displacement along the fault, the body wave analysis suggests that the earthquake consists of as many as 10 independent events, each having a seismic moment of 1.3-5.3×1026 dyn cm and a fault length of about 10 km. The spatial separation of these events varies from 14 to 40 km. This multiple-shock sequence suggests that the rupture propagation is jagged and partially incoherent with an average velocity of 2 km/s. (5) The average stress drop estimated from surface waves is about 30 bars, but the local stress drop for the individual events may be significantly higher than this. (6) The complex multiple event is a manifestation of a heterogeneous distribution of the mechanical properties along the fault, which may be caused by either asperities, differences in strength, differences in pore pressure, differences in slip characteristics (stable sliding versus stick slip), or combinations of these factors. (7) This complexity has important bearing on the state of stress along transform faults and is important in assessing the effect of large earthquakes along other transform faults like the San Andreas.

Active seismic deformation in the grabens of Northern Central America and its relationship to the relative motion of the North America - Caribbean plate boundary

Article

Jul 2001
TECTONOPHYSICS

Marco Guzmán-Speziale

The active seismic deformation along the grabens of northern Central America is calculated using a method which relates relative plate velocity with the seismic strain rate tensor. The latter is, in turn, obtained from seismic moment tensors.We calculate the typical or average moment tensor from available Centroid-Moment Tensors and fault-plane solutions. This average tensor is then used to obtain the sum of moment tensors of historical and modern earthquakes reported in the literature.Both historical and modern earthquakes yield an average extension rate of 8mm/yr along the grabens of northern Central America, while the relative motion between the North America and Caribbean plates expressed along the Motagua–Polochic fault system is 20mm/yr.This result suggests that part of the seismic deformation related to the plate boundary is taken up as extension along the grabens, which play the role of fault termination structures for the Motagua–Polochic system.

Time of sinistral slip along the Polochic Fault of Guatemala

Article

Feb 1984
TECTONOPHYSICS

The Polochic fault of Guatemala and Chiapas, Mexico was a Neogene transform segment of the North American — Caribbean plate boundary, with a total sinistral slip of 130 km. Principal activity was within the interval from about 10.3 to 6.6 m.y. B.P. or less, a time bracket based upon K-Ar ages from volcanic rock clasts in the Colotenango beds of northwest Guatemala. Earliest possible movement was established from ages of volcanic rock constituents of the older Colotenango conglomerates, deposited by streams that flowed north from a terrane now in Central Guatemala and onto terrane that was subsequently offset along the Polochic fault. It is believed that the Selegua River was connected to the Chixoy River of Central Guatemala. This river system deposited the older part of the Colotenango conglomerate now in western Guatemala about 130 km west of its source area. Two volcanic clasts from the conglomerate yield ages of and m.y. The younger age is believed to set the maximum age of sedimentation of this older part of the conglomerate and is probably close in time to initiation of fault activity. Distinctive brown serpentinite clasts in the conglomerate have been shown to be petrographically, mineralogically, and geochemically similar to serpentinite from the presumed source area north of Salamá, Guatemala.

Tectonic implications of upper-crustal seismicity in Central America

Article

Randall White

Global teleseismic earthquake relocation with improved travel times and procedures for depth determination

Article

Jun 1998

We relocate nearly 100,000 events that occurred during the period 1964 to 1995 and are well-constrained teleseismically by arrival-time data reported to the International Seismological Centre (ISC) and to the U.S. Geological Survey's National Earthquake Information Center (NEIC), Hypocenter determination is significantly improved by using, in addition to regional and teleseismic P and S phases, the arrival times of PKiKP, PKPdf; and the teleseismic depth phases pP, pwP, and sP in the relocation procedure. A global probability model developed for later-arriving phases is used to independently identify the depth phases. The relocations are compared to hypocenters reported in the ISC and NEIC catalogs and by other sources. Differences In our epicenters with respect to ISC and NEIC estimates are generally small and regionally systematic due to the combined effects of the observing station network and plate geometry regionally, differences in upper mantle travel rimes between the reference earth models used, and the use of later-arriving phases. Focal depths are improved substantially over most other independent estimates, demonstrating (for example) how regional structures such as downgoing slabs can severely bias depth estimation when only regional and teleseismic P arrivals are used to determine the hypocenter. The new data base, which is complete to about Mw 5.2 and includes all events for which moment-tenser solutions are available, has immediate application to high-resolution definition of Wadati-Benioff Zones (WBZs) worldwide, regional and global tomographic imaging, and other studies of earth structure.

Geologic-tectonic map of the Caribbean Region

Article

Jan 1980

Caribbean–Americas plate boundary in Guatemala and southern Mexico as seen on Skylab IV orbital photography

Article

Jan 1975
GEOLOGY

Skylab photographs of Guatemala clearly show the prominent fault zones that have acted as the Caribbean-Americas plate boundary. The present boundary, the Cuilco-Chixoy-Polochic fault zone, can now be extended westward into Mexico where it apparently bifurcates into northwest-trending and southwest-trending forks. The southwest-trending fork separates regions of different seismicity and volcanism and is proposed as the present plate boundary. The eastern end of the Cuilco-Chixoy-Polochic fault zone abuts a pair of faults that trend N60°E and bound Lago de Izabal. These faults bound a graben that has the shape of a parallelogram. This shape is repeated along the eastern Motagua fault zone and offshore in the adjacent part of the Bartlett Trench.The wedge of the Caribbean plate between the Americas and Cocos plates (southern Guatemala, El Salvador, and western Honduras) is being fragmented by east-west extension. Individual fragments are being slightly rotated counterclockwise as a result of a northward component of motion of eastern Honduras.

Rupture processes of some complex earth-quakes in southern Mexico

Article

Jan 1978

Jaime Yamamoto

A sequence of earthquakes occurred near the coast of Chiapas, Mexico on April 29, 1970. The long-period P waveforms of the three most important events of this sequence were analyzed using synthetic seismograms. Perturbations in the wave forms are shown to be caused by near-source structure and are produced by complexities in the earthquake source time-functions. The results show that the aftershock of April 30 at 0833 (M sub S = 6.4) can be modelled by a simple point source with a seismic moment of 6.6 x 10 to the 25th power dyne-cm. The foreshock of April 29 at 1122 (M sub S = 6.3) consisted of two simple events 7 seconds apart having approximately the same seismic moment of 4.1 x 10 to the 25th power dyne-cm. Four events were identified within the 15 second interval prior to the main rupture (M sub S = 7.3) for which the seismic moment was 9.9 x 10 to the 26th power dyne-cm.

Large‐magnitude Central American earthquakes, 1898–1994

Article

Dec 1996
GEOPHYS J INT

We have collected and re-examined macroseismic information for large Central American earthquakes since the beginning of the period of instrumental recording about one hundred years ago, and combined this with a reassessment of early instrumental information to produce a catalogue of 51 events that, we believe includes ail those with magnitudes (Ms) greater than 7.0. We have reassessed surface-wave magnitudes by consulting station bulletins and we have derived a correction that gives an equivalent Ms for events of intermediate depth. We have also developed a regional relationship between Ms and seismic moment, which enables us to estimate the seismic slip rate across the Middle American Trench. Our best estimates give an average slip rate several times smaller than suggested convergence rates, but with the seismic slip in the central segment of the trench almost an order of magnitude smaller than that in the segments on either side. The low seismic slip rate may indicate aseismic crustal deformation

Strike-slip faults and K-alkaline volcanism at El Chich??n volcano, southeastern Mexico

Article

Sep 2004
J VOLCANOL GEOTH RES

El Chichón volcano is located in the northern part of the State of Chiapas in southeastern Mexico. The volcano is situated within the Transcurrent Fault Province characterized by a series of rising and sinking blocks bounded by sinistral strike-slip faults. The basement around El Chichón is a sequence of Jurassic evaporates, Cretaceous limestones, and Tertiary terrigenous rocks folded into open and an echelon structures. The main structures in the area are the La Union and Caimba anticlines, and the Buena Vista syncline. The region is cross-cut by two conjugate fault systems: a dextral strike-slip N–S–trending set, and a sinistral strike-slip E–W set. The most significant fault of the latter system is the San Juan Fault, which controlled the emplacement of a basaltic dike near the village of Chapultenango some 1.1 Ma ago and the activity of El Chichón during the last 0.2 Ma. Additionally, a series of N45°E–trending faults (Chapultengo Fault System) have produced a half-graben geometry of blocks, on top of which El Chichón has been emplaced. Microstructures such as slickensides, tension fractures, layer-parallel slip, stylolites, and macro- and meso-folds of the sedimentary rocks, indicate that, during the late Miocene the El Chichón area was affected by a maximum principal stress (σ1) oriented N70°E, a minimum principal stress (σ3) oriented N20°W, and a vertical intermediate principal stress. This stress pattern indicates that the area underwent a strike-slip motion that produced widespread deformation. The occurrence of crustal earthquakes (<40 km) in the region with sinistral strike-slip focal mechanisms oriented along the major faults suggests that the same tectonic regime has been occurring in southern Mexico from the late Miocene to the Recent, controlling the emplacement and activity of El Chichón since its beginning during the Pliocene to Recent. This tectonic setting has produced K-alkaline trachyandesites (55–59% wt. SiO2), and K-rich trachybasalts (46–49% wt. SiO2) in the area represented by the 1.1 Ma fissural Chapultenango basalt, and by mafic enclaves. Despite this alkaline nature, El Chichón magmas display enrichments in K2O, Rb, and Sr typical of continental arc magmatism.

Neogene north American-Caribbean plate boundary across Northern Central America: Offset along the polochic fault

Article

Dec 1983
TECTONOPHYSICS

Burke Burkart

The Polochic fault was a segment of the North American-Caribbean plate boundary across Central America in the Neogene. Its 130 km of left slip was previously determined by matching structures and stratigraphie outcrop patterns of northwest and central Guatemala across the fault. Additional support for the model and the youthfulness of the recorded offset comes from an essentially perfect match of major geomorphic features across the fault. A reconstruction process which eliminates 123 km of left slip brings together rivers and drainage divides that existed before the Polochic became active.

Estructura geológica, historia técnica y morfología de América Central

Article

Jan 1968

Gabriel Dengo

Tectonic development of the Ixtapa graben, Chiapas, Mexico /

Article

Thesis (Ph. D.)--University of Texas at Austin, 1991. Vita. Includes bibliographical references (leaves 290-308).

Geophagy in Central America

Article

Feb 1984

A pre-Columbian geophagical shrine at Santiago de Esquipulas, Guatemala, was sanctified by the Christian Church. The eating of holy clay tablets diffused from this shrine throughout Central America and as far north as New Mexico. This study focuses on the consumption of holy clay tablets by pregnant Garifuna (Black Carib) in Belize. The practice provided 17 to 55% of recommended pregnancy supplementation of calcium, magnesium, zinc and iron as well as quantities of copper, manganese, selenium, potassium, nickel, and cobalt.-Authors

Tectonic Aspects of the Guatemala Earthquake of 4 February 1976

Article

Oct 1976

George Plafker

The locations of surface ruptures and the main shock epicenter indicate that the disastrous Guatemala earthquake of 4 February 1976 was tectonic in origin and generated mainly by slip on the Motagua fault, which has an arcuate roughly east-west trend across central Guatemala. Fault breakage was observed for 230 km. Displacement is predominantly horizontal and sinistral with a maximum measured offset of 340 cm and an average of about 100 cm. Secondary fault breaks trending roughly north-northeast to south-southwest have been found in a zone about 20 km long and 8 km wide extending from the western suburbs of Guatemala City to near Mixco, and similar faults with more subtle surface expression probably occur elsewhere in the Guatemalan Highlands. Displacements on the secondary faults are predominantly extensional and dip-slip, with as much as 15 cm vertical offset on a single fracture.

Neogene Caribbean Plate rotation and associated Central American tectonic evolution

Article

Jan 1984

Presents a reconstruction which juxtaposes N Central America and S Mexico by strike slip motion. Proposes that seafloor spreading began in the Cayman Trough at 30+ or -5Ma and that subsequently there was 1100km of relative plate displacement at an average rate of 3.7+ or -0.6cm/yr. This Neogene plate motion cannot be achieved by rigid plate rotation about a single pole, which implies that Central America must have rotated anticlockwise relative to the rest of the plate. The suggestion of an originally E trending arc in S Central America is more consistent with the timing and geometry of the collision of Panama with N Colombia and the resultant deformation then were earlier models that depicted collision of a N trending arc.-from Authors

Carta Geológico-Minera Tuxtla Gutiérrez E15-11, Scale 1:250,000 U–Pb zircon geochronol-ogy of Paleozoic units in Western and Central Guatemala: insights into the tectonic evolution of Middle America The geology of the Caribbean plate: Geological Society

Jan 1993
295-313

R L Sedlock
F Ortega-Gutiérrez
R C Speed
L A Solari
F Ortega-Gutiérrez
M Elías-Herrera
P Schaaf
M Norman

Sedlock, R.L., Ortega-Gutiérrez, F., Speed, R.C., 1993. Tectonostratigraphic terranes and tectonic evolution of Mexico: Geological Society of America Special Paper, vol. 278. 153 pp. Servicio Geológico Mexicano (2005), Carta Geológico-Minera Tuxtla Gutiérrez E15-11, Scale 1:250,000. Solari, L.A., Ortega-Gutiérrez, F., Elías-Herrera, M., Schaaf, P., Norman, M., Torres deLeón, R., Ortega-Obregón, C., Chiquín, M., Morán-Ical, S., 2009. U–Pb zircon geochronol-ogy of Paleozoic units in Western and Central Guatemala: insights into the tectonic evolution of Middle America. In: Pindell, J., James, H.J.K. (Eds.), The geology of the Caribbean plate: Geological Society [London] Special Publication, vol. 328, pp. 295–313. 2009.

Beyond the Motagua and Polochic faults: Active strike-slip faulting along the Western North America–Caribbean plate boundary zone

Abstract

No full-text available

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