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(a) Map of the Somma-Vesuvius volcanic complex with main structural features (UTM projection). Thin lines represent faults, fractures, and scarps; the thick line marks the Somma caldera rim (data from Ventura and Vilardo, 1999). Circles indicate the locations of the analog seismic stations of the permanent monitoring network; triangles mark the locations of the temporary digital stations. (b) North-south-striking geological cross-section of Somma-Vesuvius, showing the hypocenter distribution of earthquakes.
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Seismic monitoring of active volcanoes is an important tool for detecting fluid migration related to magmatic activity. Since the last eruption in 1944, the features of the seismic activity affecting the Somma-Vesuvius volcano (southern Italy) as well as independent geological and geophysical constraints suggest that magmatic processes are not dire...
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Context 1
... present-day Vesuvius crater grew during the 1944 eruption. The volcano is affected by two main fault systems striking northwest-southeast and northeast-southwest (Figure 1a; Bianco et al., 1998 mic anisotropy study indicates that the northwest-southeast fault system propagates down to 6 km below sea level (b.s.l., Bianco et al., 1998). The northwest-southeast and northeast- southwest faults affect both the volcanic (submarine lavas and dikes) and the sedimentary (limestones and dolomites) base- ments of the volcano. ...
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... are radio-telemetered to the central monitoring center located in Naples, where they are digitized and recorded by a PC-based system. During periods of in- creased seismicity, up to seven digital local recording stations are temporarily deployed to enhance the permanent network ( Figure 1a). ...
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... hypocentral depth of these earth- quakes ranges from the top of the crater down to about 6 km b.s.l. (Figure 1b). Clustering occurs between 2 and 3 km b.s.l. ...
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... Gutenberg-Richter b-coefficient increases from 0.8 at the top of the edifice to 1.3 at 2 to 3 km depth and then decrea- ses to 1.0 at a depth of 6 km ). Both the clustering of hypocenters and the highest b-values appear to occur at the lithological interface between the volcanics and the carbonates of the sedimentary basement (Figure 1b; Cassano and La Torre, 1987). ...
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... α is diffusivity and r is the distance at which the trig- gering front has arrived at time t. Since the hypocenters are tightly clustered along a vertical axis (i.e., the crater axis; Figure 1b), r can be substituted by source depth. Our pro- cedure for fitting equation (1) with hypocenter data is to select the deepest earthquakes that occurred in consecutive, not over- lapping, 7-day-long spans. ...
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Citations
... Fluid injections are considered as the responsible for triggering earthquake swarms in many volcanic areas of the world (Chiodini et al., 2017;Massin et al., 2013;Padrón et al., 2021;Saccorotti et al., 2002) and intraplate geothermal environments (Hainzl & Fischer, 2002;Parotidis et al., 2003). This hypothesis has been confirmed by experimental results at laboratory scale (Cebry & McLaskey, 2021) and inspired models for swarm triggering (Hill, 1977). ...
Seismic swarms are defined as a group of earthquakes occurring very close in time and space but without any distinctively large event triggering their occurrence. Up to now no simple law has been found to describe the swarm occurrence rate. Here we find an expression able to fit the average occurrence rate on some volcanic areas. This expression exhibits some differences in respect to the classical Omori law. Namely the c parameter of the Omori law is equal to zero and the power law decay of the average occurrence rate of the earthquakes is followed by an exponential decaying regime. Both the results can be interpreted in term of fluid injection and/or movements. Indeed this is a more impulsive phenomenon compared to the occurrence of a large earthquake, with a duration compatible with a c = 0. The exponential decay following the power law one could be explained by a viscoelastic relaxation of the stress induced by the injection and/or movements of fluids in the earth crust.
... Atakan et al., 1994;Rabak et al., 2010;Špičák, 2000), ou région volcanique (e.g. Benoit and McNutt, 1996;Bianco et al., 2004;Saccorotti et al., 2002). Ils peuvent aussi avoir plusieurs origines : naturelle (e.g. ...
The Ubaye region, located in the Alps at mid-distance between Grenoble and Nice, is one of the most seismically active areas in France. One of the strongest earthquakes recorded in mainland France occurred on April 5, 1959 (MLLDG 5.3). This region is characterized by a particular seismic activity composed of intertwined mainshock/aftershocks and seismic swarm sequences, involving the complex interaction of several driving processes (stress transfer, fluid-pressure, etc). Some swarms contained earthquakes of magnitude greater than 4, like the 2012-2015 swarm, which is characterized by two mainshocks: MLLDG 4.8 (26/02/2012) and MLLDG 5.2 (07/04/2014). This PhD aims at better understanding the processes that drive the seismicity and relate it to known structures in the region. The study of historical and instrumental seismicity allowed to highlight the most active areas than others (Le Lauzet, Larche, Barcelonnette, St-Paul-sur-Ubaye, Guillestre) since the 18th century. Unfortunately, the uncertainties of location and our lack of knowledge of deep structures make it very difficult to relate outcropping faults with seismicity. We then focused on the two months aftershocks that followed the April 7, 2014 earthquake. The aftershock locations distribute in a wide volume around the main fault plane. The complex spatial organization of the seismicity was quantitatively analysed through the study of the geometry of the families that composed it and confirmed by the computation of 100 focal mechanisms. During the different crisis periods (2003-2004 & 2012-2015), the presence of fluids was highlighted as one of the main drivers to explain the behaviour of the seismicity. We then decided to calculate the fluid-overpressures required to trigger each event by inverting the focal mechanisms and the stress-state. Three main results emerge: 1) the majority of events (65%) requires between 15 and 40 MPa of fluid-overpressure; 2) the strongest earthquakes also require fluid-overpressures; 3) the temporal evolution of overpressure is an indicator of the type of seismic sequence. From these results, a conceptual model is proposed to conciliate fluid and the complex behaviour of the seismicity based on the fault-valve behaviour (Sibson, 1990). After concentrating only on the 2014 crisis, I focused on the 2010-2019 period to link the pre-existing structures of the region to the 2012-2015 crisis chronology. A new relocation of the seismicity is then performed on this period starting from the LDG catalogue. The full Ubaye region seems affected by swarms and more particularly the Ubaye Valley. Moreover, the alignment of the seismicity allows us to hypothesize two faults intersecting in the area of the 2012-2015 swarm. The statistical study of the magnitude distribution (exponent b of the Gutenberg-Richter law) has identified a generic temporal behaviour for swarms marked by an increase followed by a decrease in the exponent b, associated with a fluid pressure process. The variation of the b-exponent is more complex for mainshock/aftershocks, with decreases before/after as well as increases after the mainshock. The analysis of these different results allowed us to better understand the sequence of seismic events (mainshock/aftershocks and swarms) and gave us information on the organization of active structures in the Ubaye region. This improved understanding of the complex processes at play might then help improving the risk analysis in this area.
... The first observation suggests a propagation of the source, that becomes slightly closer to LVN with time. Source migration could be explained by multiple phenomena, including fault propagation, diffusive processes, and fluid and magma motions [279,29,52,88]. The second observation implies the simultaneous activation of two nearby sources. This is not common in tectonic sequences, and would suggest the interplay with hydrothermal or volcanic fluids. ...
Deception Island is an active volcano located in the South Shetland Islands, Antarctica. Although the last eruptions occurred in 1967-1970, the volcano has undergone periods of seismic unrest in 1992, 1999, and 2015. The seismic activity of the Deception Island volcano has been monitored three months per year since 1986, coincident with the austral summers. In 2008, three permanent seismic stations were installed at Deception Island, Livingston Island, and Cierva Cove, Antarctica. The present thesis has aimed to exploit the continuous seismic record at Deception Island since 2008 (including the southern winter periods) to study the long-term seismic activity of the volcano, in order to improve our understanding of the behavior, seismicity and the mechanisms that generate the volcanic activity. It also allow us to model the S-wave velocity structure of the shallow layers of the island, as well as their characteristics. From this seismological study of the activity and structure of the Deception Island volcano, we have obtained the following results: (1) Determination of 1D models of the shallow structure along the coast and inner bay of Deception Island. Long series of ambient noise recordings from di erent land and marine stations have been used, thereby improving noise studies observing the stability of the peaks. (2) Identi cation of a new seismic signal called DLDS, using an approach based on the evaluation of the average seismic energy contained in selected frequency bands. Continuous records from permanent stations are used for DLDS detection. Due to its long duration and seasonal modulation, the analysis of DLDS require a su cient amount of seismic data throughout the year. (3) A precursory swarm of distal VT earthquakes has been identi ed. The swarm occurred SE of Livingston Island, and started ve months before the 2015 seismic crisis at Deception Island. (4) Recognition of an annual modulation for part of the seismicity at Deception Island. This annual modulation is related to the seasonal cycle and other atmospheric variations, in uenced by external factors, which can induce pressure variations in volcanic/hydrothermal uids, or be an indicator of climatic trends. (5) Identi cation of a generalized increase of the seismic activity, starting in 2011 and accelerating during 2011-2014, reaching a climax during the seismic crisis recorded at Deception Island in 2015. (6) A volcanological model is proposed for the behaviour of Deception Island during the 7.5 years preceding the 2015 crisis. The volcano is in a dormant state up to 2010 (Phase 1), with a low level of seismic activity. In 2011 the activity shifts to an awakening state (Phase 2) characterized by a gradual increase in seismic activity as a consequence of a deep magmatic intrusion that increases the amount of gas permeating the volcanic edi ce. Finally, in 2014-2015 the volcano becomes restless (Phase 3) and the activity accelerates, suggesting the occurrence of a failed eruption. (7) The availability of continuous seismic data at Deception Island, even with just one station (DCP), allows for a qualitative leap in our ability to characterize and understand volcanic behaviour. This emphasizes the need for a permanent seismic network at Deception Island for the assessment of volcanic hazards.
... From the hypocenter distribution, the Pesawaran swarms are caused by the activity of the Menanga Fault [1]. In nature, swarms are generally related to the fluid activity around the volcanic area [9] [10], geothermal activity [11] and human induced [12]. This approach aims to confirm the mechanism of swarms occurrence, whether it is correlated to the volcanic-fluid activity or purely tectonic fault movement of Menanga. ...
... The relationship between the diffusivity of hypocenter migration and swarm duration shown in Fig. 4a is for earthquake swarms in northeastern Japan. We additionally investigated the relation under various tectonic environments from the result of previous studies (Saccorotti et al. 2002;Parotidis et al. 2003; Hill and Prejean . We used swarm durations either cited or estimated from the time series in the literature. ...
Earthquake swarms exhibit highly uncertain temporal behavior. We investigated the relationship between the swarm duration and the diffusivity of hypocenter migration for triggered earthquake swarms in northeastern Japan. These parameters were systematically estimated by applying a diffusion model and using a unified definition of time windows for the initial and final stages of swarm activity. This approach detected a clear negative correlation between the diffusivity and swarm durations. The relation follows a power-law with an exponent of -0.5 to -1.0. Examination of published data confirmed that this relationship globally holds under various localities and tectonic environments. These results suggest that diffusivity, and by extension, crustal permeability and fluid viscosity play a key role in controlling the duration of the fluid-driven swarms.
... As a general rule, the Naples Bay is composed of three main volcanic and physiographic domains: the Somma-Vesuvius volcano and its offshore, the Phlegrean Fields and the Gulf of Pozzuoli and the Island of Ischia and Procida [20] . The Somma-Vesuvius volcano has been deeply studied regarding the eruptive events, the recent seismicity, the geochemistry, the ground movements of the volcano and the volcanic hazard [21][22][23][24][25][26] . The Phlegrean Fields and the Gulf of Pozzuoli, i.e., the submerged border of the Phlegrean caldera, have also been studied by many authors and are continuously monitored by the National Institute of Geophysics and Volcanology (INGV). ...
Marine geological maps of the Campania region have been constructed both to a 1:25.000 and to a 1:10.000 scale in the frame of the research projects financed by the Italian National Geological Survey, focusing, in particular, on the Gulf of Naples (Southern Tyrrhenian Sea), a complex volcanic area where volcanic and sedimentary processes strongly interacted during the Late Quaternary and on the Cilento Promontory offshore. In this paper, the examples of the geological sheets n. 464 “Isola di Ischia” and n. 502 “Agropoli” have been studied. The integration of the geological maps with the seismo-stratigraphic setting of the study areas has also been performed based on the realization of interpreted seismic profiles, providing interesting data on the geological setting of the subsurface. The coastal geological sedimentation in the Ischia and Agropoli offshore has been studied in detail. The mapped geological units are represented by: i) the rocky units of the acoustic basement (volcanic and/or sedimentary); ii) the deposits of the littoral environment, including the deposits of submerged beach and the deposits of toe of coastal cliff; iii) the deposits of the inner shelf environment, including the inner shelf deposits and the bioclastic deposits; iv) the deposits of the outer shelf environment, including the clastic deposits and the bioclastic deposits; v) the lowstand system tract; vi) the Pleistocene relict marine units; vii) different volcanic units in Pleistocene age. The seismo-stratigraphic data, coupled with the sedimentological and environmental data provided by the geological maps, provided us with new insights on the geologic evolution of this area during the Late Quaternary.
... Higher magnitude shallow seismicity has been related to fluid-driven rock fracturing triggered by pressure variation in the shallow aquifer 1,18 . The deeper earthquakes, which occur preferentially in high-energy seismic swarms, have higher magnitudes (up to 3.6 for the earthquake recorded on October 9th 1999), and are mainly related to the interaction of the regional and local stress field, as well as fluid circulation in the hydrothermal system 1,16,18,20 . Between the 1999-2000 and the end of 2011, seismicity consisted mainly of low-magnitude earthquakes within the shallow volume 18 . ...
... Stress changes related to fluid circulation could have driven the LP activity in the southeastern sector of the volcano, as well as the downward migration of the hypocenters of the VT sequence. It is likely that, as observed in other volcanoes, the direction of earthquake migration reflects the pattern of the fluid circulation 4,6,16 . Assuming that the seismic sequence of November/December 2018 can be modelled as a process of pore pressure diffusion 34 , we calculated the hydraulic diffusivity, D, by fitting the rate of deepening of the hypocenters to the equation: ...
We reconstruct the composite dynamics of Mt. Vesuvius volcano in the period 2012-2019 from the study of ground deformation, seismicity, and geofluid (groundwater and fumarolic fluids) circulation and recognize complex spatio-temporal variations in these observables at medium (years) and short (months) timescales. We interpret the observed patterns as the combined effect of structural changes affecting the volcanic edifice and variations of the dynamics of the hydrothermal system. In particular, we identify a change in the activity state of Mt. Vesuvius. After the activity reached minimum levels in 2014, the centroid of the surface manifestations migrated towards the SE. Episodic variations of co-seismic and aseismic deformation and fluid release, if analysed separately, would likely have been interpreted as pseudo-random oscillations of the background geophysical and geochemical signals. When organised in a comprehensive, multiparametric fashion, they shed light on the evolution of the volcano in 4D (x,y,z, time) space. These inferences play a crucial role in the formulation of civil protection scenarios for Mt. Vesuvius, a high risk, densely urbanized volcanic area which has never experienced unrest episodes in the modern era of instrumental volcanology.
... As a general rule, the Naples Bay is composed of three main volcanic and physiographic domains: the Somma-Vesuvius volcano and its offshore, the Phlegrean Fields and the Gulf of Pozzuoli and the Island of Ischia and Procida [20] . The Somma-Vesuvius volcano has been deeply studied regarding the eruptive events, the recent seismicity, the geochemistry, the ground movements of the volcano and the volcanic hazard [21][22][23][24][25][26] . The Phlegrean Fields and the Gulf of Pozzuoli, i.e., the submerged border of the Phlegrean caldera, have also been studied by many authors and are continuously monitored by the National Institute of Geophysics and Volcanology (INGV). ...
Marine geological maps of the Campania region have been constructed both to a 1:25.000 and to a 1:10.000 scale in the frame of the research projects financed by the Italian National Geological Survey, focusing, in particular, on the Gulf of Naples (Southern Tyrrhenian Sea), a complex volcanic area where volcanic and sedimentary processes strongly interacted during the Late Quaternary and on the Cilento Promontory offshore. In this paper, the examples of the geological sheets n. 464 "Isola di Ischia" and n. 502 "Agropoli" have been studied. The integration of the geological maps with the seismo-stratigraphic setting of the study areas has also been performed based on the realization of interpreted seismic profiles, providing interesting data on the geological setting of the subsurface. The coastal geological sedimentation in the Ischia and Agropoli offshore has been studied in detail. The mapped geological units are represented by: i) the rocky units of the acoustic basement (volcanic and/or sedimentary); ii) the deposits of the littoral environment, including the deposits of submerged beach and the deposits of toe of coastal cliff; iii) the deposits of the inner shelf environment, including the inner shelf deposits and the bioclastic deposits; iv) the deposits of the outer shelf environment, including the clastic deposits and the bioclastic deposits; v) the lowstand system tract; vi) the Pleistocene relict marine units; vii) different volcanic units in Pleistocene age. The seismo-stratigraphic data, coupled with the sedimentological and environmental data provided by the geological maps, provided us with new insights on the geologic evolution of this area during the Late Quaternary.
... Somma) and an intra-caldera cone (Mt. Vesuvius) [34][35][36][37][38][39][40][41][42][43][44]. Volcanic activity in the area started 400 ka B.P. The Somma-Vesuvius volcanic succession mainly consists of lava flows, interbedded with strombolian scoria fall deposits (aged between 39 and 25 ka; Santacroce, 1987) overlain by the deposits of four main plinian eruptions-(i) Pomici di Base/Sarno (18 ka B.P.); (ii) Mercato/Ottaviano Pumice (8 ka B.P.); (iii) Avellino Pumice (3.5 ka B.P.); and (iv) Pompeii Pumice (79 CE). ...
Submarine canyons are geomorphologic lineaments engraving the slope/outer shelf of
continental margins. These features are often associated with significant geologic hazard when they develop close to densely populated coastal zones. The seafloor of Naples Bay is deeply cut by two incisions characterized by a dense network of gullies, namely the Dohrn and Magnaghi canyons, which develop from the shelf break of the Campania margin, down to the peripheral rise of the Eastern Tyrrhenian bathyal plain. Seismic-stratigraphic interpretation of multichannel seismic reflection profiles has shown that quaternary tectonics and recent to active volcanism have exerted a significant control on the morphological evolution and source-to sink depositional processes of the
Dohrn and Magnaghi submarine canyons. The Dohrn canyon is characterized by relatively steep walls hundreds of meters high, which incise a Middle-Late Pleistocene prograding wedge, formed by clastic and volcaniclastic deposits associated with the paleo-Sarno river system during the Mid-Late Pleistocene. The formation of the Dohrn canyon predates the onset of the volcanic eruption of the Neapolitan Yellow Tuff (NYT), an ignimbrite deposit of ca. 15 ka that represents the bedrock on which the town of Napoli is built. Integrated stratigraphic analysis of high-resolution seismic profiles and
marine gravity core data (C74_12) collected along the flanks of the eastern bifurcation of the head of Dohrn Canyon suggests that depositional processes along the canyon flanks are dominated by gravity flows (e.g., fine-grained turbidites, debris flows) and sediment mass transport associated with slope instability and failure.
... The presence of fluids, within the hydrothermal system of Mt. Vesuvius, plays a fundamental role in modulating the occurrence of earthquakes (Saccorotti et al., 2002;Madonia et al., 2008;Cusano et al., 2013a, b). After the 1999-2000 crisis, the seismicity of Mt. ...
We present a detailed analysis of the low frequency
seismicity occurred at Mt. Vesuvius in the time range 2003–2018. This kind
of seismicity is atypical for the volcano and poorly studied, therefore we
characterized it in terms of spectral analysis, waveform cross-correlation,
location and polarization properties. The different decay patterns of the
spectra, the existence of both earthquake families as well as single events,
the relatively wide seismogenic volume inferred from the locations and
polarization features, indicate that the events are caused by distinct
source mechanisms: slow brittle failure in dry rocks and resonance of
fluid-filled cracks. On these basis, we classified the earthquakes as Low
Frequency (LF) and Long Period (LP). Despite the differences between the two
classes, both the event types are ascribable to the dynamics of the deep
hydrothermal reservoir which induces variations of the fluid pore pressure
in the medium. The fluid amount involved in the generation process, as well
as the physical-chemical properties of the surrounding rocks are the
essential factors that control the occurrence of a mechanism rather than the
other.
