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(a) Tectonic setting of the M w 8.4 2001 southern Peru earthquake. (b) The 1-day aftershocks of the earthquake, together with the rupture areas of the previous earthquake in the region outlined in grey. Arrows show the direction of plate convergence (from DeMets et al. (1994) ), its length showing the plate velocity. (c) Contoured satellite-derived gravity fi eld of Sandwell and Smith (1997)-Version 15.2-off-shore of the Peru earthquake, and the slip distribution about 42 s after rupture initiation shown. (d) Same as (c) but with the fi nal co-seismic slip in the earthquake plotted. Symbols, etc. are as in Fig. 2
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Improvements in the quality and quantity of seismological data, together with technological advances in marine geophysics,
mean that we are now able to examine in detail the infl uence of sea fl oor topography on the rupture process of great subduction
earthquakes. Subducting seamounts were first suspected to affect the rupture process of a great e...
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Context 1
... 2001 southern Peru earthquake occurred on a 400 km long fault dipping 15°, within a ∼1,000 km long seismic gap on the plate boundary where the Nazca plate subducts under the South American plate. Figure 4 illustrates the tectonic setting of the earth- quake. The history of known earthquakes in the region (Fig. 5) shows that earthquakes in the southern Peru region has been followed within about a decade by one in northern Chile, more than once in known history. ...
Context 2
... to the time-history, the region to the south of the 2001 Peru earthquake is a candidate for earthquake around 2010 1947 1967 1928 1905 1911 1933 1945 1956 1988 1979 1922 1913 1906 suggest, increases the coupling between the two sides of the fault, resulting in a highly heterogeneous earth- quake rupture history. The aftershock distribution (Fig. 4) was found to be very non-uniform over the fault, and the trapezoidal shape of the fi rst asperity coincides with a trape zoidal region of lower after- shock density, visible both in the 24-h and the 6-month aftershock distributions ( Robinson et al. 2006). This is in contrast to the usual observation that regions of higher slip have ...
Citations
... Кроноцкое землетрясение и сегментация островодужного склона. Имеющиеся геолого-геофизические данные свидетельствуют о том, что очаги сильнейших землетрясений, бреши и кластеры в распределении землетрясений могут быть связаны с сегментами в нависающей плите и/или тектоническими элементами на пододвигающейся плите [17,23]. Последние включают в себя подводные горы, вулканические хребты и зоны разломов, которые влияют на особенности сцепле-Рис. ...
... ния между пододвигаемой и нависающей плитами в зонах субдукции. Эти структуры играют важную роль в процессе распространения разрыва при землетрясениях, являясь барьерами, через которые разрыв не распространяется, или шероховатостями (asperities), к которым приурочены основные толчки и на которых происходит основной сброс напряжений [17,23,31,37,47]. Исследование Кроноцкого землетрясения 05.12.1997 г. (M w = 7.9) показало, что его очаг охватил три сейсмоактивных сегмента [1][2][3]. ...
Abstract—The specific morphology of the inner and outer slopes of the eastern Kuril–Kamchatka Trench
were revealed based on joint study of bathymetry and seismic profiles obtained in two RV “Sonne” cruises
and previous investigations. Three segments of ocean floor differing in relief, thickness of sediments and tectonic
activity were distinguished on the outer slope. Their subduction under Eastern Kamchatka governs the
recent morphology of the accretionary wedge in the area between the Krusenstern Fault and Uglovoe Rise.
The Krusenstern Fault, Obruchev Rise, and Naturalist Fault control segmentation of the trench’s island
slope and seismic regime in this section of Kuril–Kamchatka subduction zone.
Keywords:
... Contreras-Reyes et al. (2019) processed wide angle seismic data, gravity modelling and seismological constraints, and explain the role of the uplifted and smooth seafloor topography of the Nazca Ridge on subduction erosion processes off Peru. Southern Peru is particularly interesting, since as Das & Watts (2009) stated earthquakes in the southern Peru region have been followed by one in northern Chile within about a decade, more than once in known history. Both earthquakes, the 2001 southern Peru and the 2014 Iquique earthquake occurred on the same seismic gap on the plate boundary between the Nazca Plate and the South American Plate. ...
The Northern Chilean subduction zone is characterized by long-term subduction erosion with very little sediment input at the trench and the lack of an accretionary prism. Here, multichannel seismic reflection (MCS) data were acquired as part of the CINCA (Crustal Investigations off- and onshore Nazca Plate/Central Andes) project in 1995. These lines cover among others the central part of the MW 8.1 Iquique earthquake rupture zone before the earthquake occurred on 1 April 2014. We have re-processed one of the lines crossing the
updip parts of this earthquake at 19◦40�S, close to its hypocentre. After careful data processing and data enhancement, we applied a coherency-based pre-stack depth migration algorithm, yielding a detailed depth image. The resulting depth image shows the subduction interface prior to the Iquique megathrust earthquake down to a depth of pproximately 16 km and gives detailed insight into the characteristics of the seismogenic coupling zone. We found significantly varying interplate reflectivity along the plate interface which we interpret to be caused by the comparably strong reflectivity of subducted fluid-rich sediments within the grabens and half-grabens that are predominant in this area due to the subduction-related bending of the oceanic plate. No evidence was found for a subducted seamount associated to the Iquique Ridge along the slab interface at this latitude as interpreted earlier from the same data set. By comparing relocated fore- and aftershock seismicity of the Iquique earthquake with the resulting depth image, we can divide the continental wedge into two domains. First, a frontal unit beneath the lower slope with several eastward dipping back-rotated splay faults but no seismicity in the upper plate as well as along the plate interface. Secondly, a landward unit beneath the middle slope with differing reflectivity that shows significant seismicity in the upper plate as well as along the plate interface. Both units are separated by a large eastward dipping mega splay fault, the root zone of which shows diffuse seismicity, both in the upper plate and at the interface. The identification of a well-defined nearly aseismic frontal unit sheds new light on the interplate locking beneath the lower continental slope and its controls.
... Since then, the topic of seafloor roughness and megathrust earthquakes has been addressed by many studies. Improved methods for slip inversions (e.g., Mai and Thingbaijam, 2014;Ye et al., 2016;Hayes, 2017), the increased coverage and precision of GPS stations (e.g., Métois et al., 2012), technological advances in marine geophysics (Das and Watts, 2009;Kopp, 2013), but also the occurrence of relatively many M W > 8.5 events over the past decades (e.g., Okal, 2007, 2011;Lay, 2015) all contributed to a better understanding of this relationship. Most studies that address the possible influence of seafloor roughness on rupture dynamics focus on the role of a single bathymetric feature, sometimes even considering a single seismic event. ...
... There are several natural examples of seamounts that are thought to have promoted the occurrence of megathrust earthquakes (von Huene et al., 2000;Abercrombie et al., 2001;Husen et al., 2002;Bilek et al., 2003;Das and Watts, 2009;Bell, 2014). von Huene et al. (2000) proposed that seamounts associated with the Fisher Seamount Chain offshore Costa Rica enter the subduction zone, where they act as asperities for moderate to large (M S ¼ 6.4-7.0) ...
The interface between the downgoing- and overriding plates in subduction zones can host very large earthquakes, depending on the characteristics of the subduction zone. One parameter that is thought to play a role in tuning this seismogenic behavior is the subduction interface roughness. The size and distribution of bathymetric features on the interface, the amount of sediments that subduct, and processes that occur during subduction all contribute to this roughness. Many studies that addressed the relationship between the roughness and seismicity of the megathrust generally converge towards a model where a smooth interface is more prone to host large- to giant events, while a rough seafloor might hinder the occurrence of earthquakes. However, contradicting examples from nature exist as well, and a detailed understanding of this relationship is still missing. This review article discusses the most important studies, first providing an overview of studies that focus on the role of specific features on the seafloor, after which several global, more general approaches will be discussed. Finally, three well-studied regions are discussed in more detail, showing the complexity of the problem, but also the large trench-parallel variability in seismogenic behavior that can occur within a single subduction zone.
... This roughness mainly results from the size and distribution of topographic features on the seafloor, such as seamounts or ridges. Many studies have already addressed the influence of subducting topography on the spatial occurrence of megathrust earthquakes (e.g., Das & Watts 2009;Kopp 2013;Wang & Bilek 2014), but a detailed understanding of how this roughness affects the state of stress at the subduction interface, and therefore its seismogenic potential, is still debated. ...
... By focusing on the spatial distribution of individual ruptures in nature, several studies have shown that a subducting seamount, ridge or fracture zone has acted as a barrier to rupture propagation (e.g., Das & Watts, 2009;Geersen et al., 2015;Henstock et al., 2016;Kodaira et al., 2000;Mochizuki et al., 2008;Robinson et al., 2006;Singh et al., 2011). In contrast, other theories suggest that a subducting feature may act as an asperity and therefore promote the occurrence of megathrust earthquakes instead (Bilek et al., 2003;Cloos, 1992;Husen et al., 2002;Scholz & Small, 1997). ...
The roughness of the subduction interface is thought to influence seismogenic behavior in subduction zones, but a detailed understanding of how such roughness affects the state of stress along the subduction megathrust is still debated. Here, we use seismotectonic analogue models to investigate the effect of subduction interface roughness on seismicity in subduction zones. We compared analogue earthquake source parameters and slip distributions for two roughness endmembers. Models characterized by a very rough interface have lower interface frictional strength and lower interseismic coupling than models with a smooth interface. Overall, ruptures in the rough models have smaller rupture area, duration and mean displacement. Individual slip distributions indicate a segmentation of the subduction interface by the rough geometry. We propose that flexure of the overriding plate is one of the mechanisms that contribute to the heterogeneous strength distribution, responsible for the observed seismic behavior.
... This roughness mainly results from the size and distribution of topographic features on the seafloor, such as seamounts or ridges. Many studies have already addressed the influence of subducting topography on the spatial occurrence of megathrust earthquakes (e.g., Das & Watts 2009;Kopp 2013;Wang & Bilek 2014), but a detailed understanding of how this roughness affects the state of stress at the subduction interface, and therefore its seismogenic potential, is still debated. ...
... By focusing on the spatial distribution of individual ruptures in nature, several studies have shown that a subducting seamount, ridge or fracture zone has acted as a barrier to rupture propagation (e.g., Das & Watts, 2009;Geersen et al., 2015;Henstock et al., 2016;Kodaira et al., 2000;Mochizuki et al., 2008;Robinson et al., 2006;Singh et al., 2011). In contrast, other theories suggest that a subducting feature may act as an asperity and therefore promote the occurrence of megathrust earthquakes instead (Bilek et al., 2003;Cloos, 1992;Husen et al., 2002;Scholz & Small, 1997). ...
The roughness of the subduction interface is thought to influence seismogenic behavior in subduction zones, but a detailed understanding of how such roughness affects the state of stress along the subduction megathrust is still debated. Here, we use seismotectonic analogue models to investigate the effect of subduction interface roughness on seismicity in subduction zones. We compared analogue earthquake source parameters and slip distributions for two roughness endmembers. Models characterized by a very rough interface have lower integrated fault strength and lower interseismic coupling than models with a smooth interface. Overall, ruptures in the rough models have smaller rupture area, duration, and mean displacement. Individual slip distributions indicate a segmentation of the subduction interface by the rough geometry. We propose that flexure of the overriding plate is one of the mechanisms that contribute to a heterogeneous stress distribution, responsible for the observed seismic behavior.
... Geometrical irregularities along the interface (i.e., the interface roughness) could create heterogeneities in seismogenic behavior, and, in turn, a segmentation of the subduction interface, as initially suggested by Kelleher & McCann (1976). Hence, the role of the subduction interface roughness, or individual topographical features on the seafloor, such as seamounts or ridges, has been studied extensively, but has not yet led to a general consensus (e.g., Das & Watts 2009). ...
... Many studies focus on the role of a single topographic feature on rupture propagation, either suggesting that it has facilitated the occurrence of an earthquake (e.g., Cloos 1992;Scholz & Small 1997;Von Huene et al. 2000;Abercrombie et al. 2001;Husen et al. 2002;Bilek et al. 2003;Das & Watts 2009;Müller & Landgrebe 2012;Bell et al. 2014;Landgrebe & Müller 2015), or that it has acted as a barrier and therefore limited rupture occurrence and propagation (e.g., Kodaira et al. 2000;Robinson et al. 2006;Mochizuki et al. 2008;Wang & Bilek 2011;Geersen et al. 2015;Marcaillou et al. 2016). The contrasting observations from these studies are perhaps the result of some limitations related to observing local natural phenomena. ...
... Besides the large scale curvature of the downgoing plate, smaller variations in the geometry of the subduction interface (i.e., seafloor features such as seamounts, ridges and plateaus) are thought to affect its seismogenic behavior as well (e.g., Das & Watts 2009;Wang & Bilek 2014). This so-called seafloor roughness is related to previously mentioned parameters like sediment thickness and structure of the forearc. ...
Subduction zones are known for their very large earthquakes, with observed magnitudes up to MW 9.6, and are therefore studied extensively by the scientific community. The impact of such events on societies can be immense, as demonstrated by the recent MW 9.1 Tohoku (2011), MW 8.8 Maule (2010) and MW 9.2 Sumatra (2004) earthquakes, which occurred in densely populated areas, causing terrible human and economic losses.
There is thus a strong need for a better understanding of the spatial and temporal occurrence of such devastating events. A parameter that has been proposed to control the seismogenic behavior in subduction zones is the roughness of the subduction interface. This roughness is the combined result of seafloor morphology of the downgoing plate, the addition of sediments during subduction, as well as processes that occur during subduction, such as tectonic erosion. A rough subduction interface is thought to promote, as well as hinder the occurrence of large interplate earthquakes. These contrasting theories make it challenging to reach a general consensus on the role played by subduction interface roughness in the seismicity in subduction zones.
This Thesis aims to provide further insights into this relationship, based on global natural data analyses and seismotectonic analogue models.
Since the roughness at the subduction interface is often unknown, the seafloor seaward of the trench is used as a proxy for the subduction interface. The seafloor facing all subduction zones is analyzed, resulting in a roughness signal at two chosen wavelength bandwidths: the short- (12-20 km) and long (80-100 km) wavelengths. Subsequently, the roughness amplitudes associated with specific features on the seafloor, such as seamounts, fracture zones or ridges, are compared with the global trend. Results show that seamounts have much larger roughness amplitudes at both wavelengths, while ridges can only be distinguished at long wavelengths. Fracture zones cannot be distinguished from the global trend. The seafloor roughness is also used to make a comparison with parameters describing the state of stress within subduction zones. A clear correlation has been observed between high seismic coupling and relatively low roughness amplitudes, as well as between low seismic coupling and relatively high seafloor roughness amplitudes.
A more detailed comparison was done by focusing on the occurrence of large interplate earthquakes in subduction zones, based on a newly compiled earthquake database, SubQuake. This database includes spatial characteristics for MW ≥ 7.5 subduction interplate events that occurred since 1900. The spatial occurrence of these ruptures, as well as their seismic asperities and epicenters, are compared with the seafloor roughness on a global scale. Results show that MW ≥ 7.5 earthquakes occur preferentially on smooth subducting seafloor at long wavelengths. This correlation is the clearest when considering great- to giant earthquakes (i.e., MW > 8.5), suggesting that a continuous smooth seafloor plays an important role in the development of such large events. Seismic asperities correspond to smoother seafloor at both wavelengths compared to rupture areas in general, while epicenters seem to correlate with slightly rougher seafloor, suggesting that the nucleation of ruptures requires different interface conditions than the ability for a rupture to propagate.
To overcome unavoidable limitations related to natural observations, such as the limited resolution or spatial coverage of the seismic imagery, or the limited sampling period, ad hoc seismotectonic analogue models have been run to study the relationship between subduction interface roughness and megathrust earthquakes as well. These models consist of a viscoelastic gelatin wedge with a 3D-printed subducting seafloor. Two seafloor roughness endmembers have been tested: a planar- and a very rough interface characterized by many large seamounts. Modelling results show that models with a rough interface have smaller earthquakes than models characterized by a smooth interface. In addition, the rough models have lower frictional interface strength and lower interseismic coupling. These results are in agreement with the results obtained in the natural data analysis.
... with large amounts of trench sediments positively correlate with the occurrence of great interplate earthquakes. This relates to another theory that developed over the years, suggesting a negative correlation between subduction interface roughness and megathrust earthquakes (Bassett & Watts, 2015;Das & Watts, 2009;Heuret et al., 2012;Kelleher & McCann, 1976;Kopp, 2013;Loveless et al., 2010;Sparkes et al., 2010;Wang & Bilek, 2014). Subduction interface roughness results from a combined effect of topographic features on the seafloor (e.g., seamounts, ridges, or plateaus), amount of sediments, and possible deformation processes occurring during subduction (e.g., tectonic erosion). ...
... pt for some regions where we take into account the obliquity of specific linear features extending into the trench (i.e., for the Joban Seamount chain in Japan, the Louisville ridge in Tonga, and the Murray Ridge in Makran). In most cases, the seafloor right in front of the trench is a good proxy for the subduction interface (Bassett & Watts, 2015;S. Das & Watts, 2009), and the use of this proxy therefore seems a reasonable assumption for this global study. The roughness data selected for the rupture, no-rupture, and seismic asperity segment groups are analyzed in terms of density distribution, illustrating which roughness amplitudes are the most common. ...
... The fact that M W ≥ 7.5 megathrust events preferably occur in regions adjacent to a smooth subducting seafloor is in agreement with previous studies (Bassett & Watts, 2015;Das & Watts, 2009;Wang & Bilek, 2014), which compared the variations in bathymetry with the occurrence of megathrust events in a qualitative way. We show that this pattern is not only true for specific ruptures or subduction zones but that it is a general pattern, mainly observed for long-wavelength seafloor roughness (Figures 9c and 9d). ...
The role of seafloor roughness on the seismogenic behavior of subduction zones has been increasingly addressed over the past years, although their exact relationship remains unclear. Do subducting features like seamounts, fracture zones, or submarine ridges act as barriers, preventing ruptures from propagating, or do they initiate megathrust earthquakes instead? We address this question using a global approach, taking into account all oceanic subduction zones and a 117-year time window of megathrust earthquake recording. We first compile a global database, SubQuake, that provides the location of a rupture epicenter, the overall rupture area, and the region where the largest displacement occurs (the seismic asperity) for MW ≥ 7.5 subduction interplate earthquakes. With these data, we made a quantitative comparison with the seafloor roughness seaward of the trench, which is assumed to be a reasonable proxy for the subduction interface roughness. We compare the spatial occurrence of megathrust ruptures, seismic asperities, and epicenters, with two roughness parameters: the short-wavelength roughness RSW (12–20 km) and the long-wavelength roughness RLW (80–100 km). We observe that ruptures with MW ≥ 7.5 tend to occur preferentially on smooth subducting seafloor at long wavelengths, which is especially clear for the MW > 8.5 events. At both short and long wavelengths, seismic asperities show a more amplified relation with smooth seafloor than rupture segments in general. For the epicenter correlation, we see a slight difference in roughness signal, which suggests that there might be a physical relationship between rupture nucleation and subduction interface roughness.
... Indeed, faults are rarely planar over length scales of tens of kilometers and in fact, fault segmentation and geometric complexity are visible at multiple scales (Candela et al., 2012). Subduction zones also show geometrical complexities like subducting seamounts (Das & Watts, 2009). It is also known that subduction zones have large normal faults that connect the main slab and can sometimes be reactivated during seismic events (Hicks & Rietbrock, 2015;Hubbard et al., 2015). ...
Active faults release elastic strain energy via a whole continuum of modes of slip, ranging from devastating earthquakes to slow slip events (SSEs) and persistent creep. Understanding the mechanisms controlling the occurrence of rapid, dynamic slip radiating seismic waves (i.e., earthquakes) or slow, silent slip (i.e., SSEs) is a fundamental point in the estimation of seismic hazard along subduction zones. Using the numerical implementation of a simple rate-weakening fault model, we show that the simplest of fault geometrical complexities with uniform rate-weakening friction properties give rise to both SSEs and fast earthquakes without appealing to complex rheologies or mechanisms. We argue that the spontaneous occurrence, the characteristics and the scaling relationship of SSEs and earthquakes emerge from geometrical complexities. The geometry of active faults should be considered as a complementary mechanism to current numerical models of SSEs and fast earthquakes.
... North of 21 • 20 N, the wedge becomes incorporated in the domain of continental margin subduction, involving progressively lower to middle Miocene slope and trench sediments (Reed et al., 1992). The southern tip of Taiwan Island represents the uplifted internal domain of the oceanic accretionary wedge currently undergoing the effects of the continental margin subduc- tion (Lundberg et al., 1997;Reed et al., 1992;Huang et al., 1997Huang et al., , 2006Chang et al., 2009). The retroside of the wedge extends offshore southward of the Hengchun Peninsula (HP) in the form of the Hengchun Ridge (HR) and Southern Longitudinal Trough (SLT) as far as 20 • 30 N Lin et al., 2009;Lester et al., 2013). ...
... In most models, the NW-SE oriented Kaoping Slope (KS) west of the subduction wedge of the Hengchun Ridge represents the part of the prism associated with the incipient subduction of the thinned Chinese continental margin (e.g. Huang et al., 1997;Liu et al., 1997;Malavieille et al., 2002;Chang et al., 2009;Malavieille and Trullenque, 2009;Mesalles et al., 2014). To the North, where the subduction of the southeastern margin of the Chinese continent is mature, the crust is now strongly deformed and rapidly uplifted in the Central Range of Taiwan (e.g., Simoes et al., 2007). ...
... This evolutionary setting (Fig. 10) has allowed the development of two different ophiolite bearing mélanges, the Kenting mélange which age range between 1 to 10 Ma and the 3.5-3.7 Ma old Lichi mélange whose formation processes are still debated. The detailed stratigraphic and structural characters and interpretations proposed for both mélange formations have been synthetized and discussed in Chang et al. (2009). The Kenting mélange is supposed to be a direct result of subduction processes acting in the forewedge. ...
Orogenic wedges locally present chaotic tectonostratigraphic units that contain exotic blocks of various size, origin, age and lithology, embedded in a sedimentary matrix. The occurrence of ophiolitic blocks, sometimes huge, in such “mélanges” raises questions on i) the mechanisms responsible for the incorporation of oceanic basement rocks into an accretionary wedge and ii) the mechanisms allowing exhumation and redeposition of these exotic elements in “mélanges” during wedge growth.
... The projected slip on the surface (Fig. 8) is correlated with the surface topography, coseismic rupture extending through the low elevation area. The role of subducted seamounts in the nucleation and rupture propagation of large subduction earthquakes has been widely discussed (Bilek et al., 2003; Das and Watts, 2009; Dixon and Moore, 2007; Hicks et al., 2012; Schurr et al., 2012; H. Yang et al., 2013 ). A series of earthquakes between 1983 and 1999 along the Costa Rican subduction zone led to the suggestion that spaced isolated seamounts could act as asperities (Bilek et al., 2003). ...
On 23rd October 2011, a MW 7.1 reverse slip earthquake occurred in the Bardakçı-Saray thrust fault zone in the Van region, Eastern Turkey. Earlier geodetic studies have found different slip distributions in terms of both magnitude and pattern. In this paper, we present several COSMO-SkyMED (CSK), Envisat ASAR and RADARSAT-2 interferograms spanning different time intervals, showing that significant postseismic signals can be observed in the first three days after the mainshock. Using observations that combine coseismic and postseismic signals is shown to significantly underestimate coseismic slip. We hence employed the CSK pair with the minimum postseismic signals to generate one conventional interferogram and one along-track interferogram for further coseismic modelling. Our best-fit coseismic slip model suggests that: (1) this event is associated with a buried NNW dipping fault with a preferable dip angle of 49° and a maximum slip of 6.5 m at a depth of 12 km; and (2) two unequal asperities can be observed, consistent with previous seismic solutions. Significant oblique aseismic slip with predominant left-lateral slip components above the coseismic rupture zone within the first 3 days after the mainshock is also revealed by a postseismic CSK interferogram, indicating that the greatest principal stress axis might have rotated due to a significant stress drop during the coseismic rupture.
