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Earthquake detection and phase picking are crucial steps in the analysis of earthquakes. With the increasing number of seismic instruments available, large amounts of seismic data are generated, requiring the use of automatic algorithms to process earthquake series and to include events that would not be discovered with manual approaches. The Petrinja earthquake series started with local magnitude ML5.0 earthquake on December 28, 2020, followed by ML6.4 earthquake one day later. In the two years of this earthquake series, human analysts picked a total of 16,000 earthquakes smaller than M2.0, 1528 with magnitudes M2.0-2.9, 156 with magnitudes M3.0-3.9, 17 with magnitudes M4.0-4.9, 2 with magnitudes M5.0-5.9 and one earthquake with magnitude greater than M6.0. While the seismic network at the onset of this sequence counted only a few instruments in the epicentral area, the rapid aftershock deployment of 5 stations in the near vicinity of the fault zone, and the further gradual yet still remarkable growth of the seismic network to more than 50 instruments, produced an extraordinary amount of data, which are perfectly suited for employing machine learning (ML) methods for seismic phase picking and earthquake detection.In this study we present application of various ML methods to the Petrinja earthquake series. We also compare how the results change when we train a model using a subset of data from this earthquake series. Our results show that these machine learning methods are promising approaches for accurately detecting and picking phases in such earthquake series, and also delineate tectonic features responsible for generating them.

14 pages, 9 figures, 3 tables, Picking arrival times of P and S phases is a fundamental and time‐consuming task for the routine processing of seismic data acquired by permanent and temporary networks. A large number of automatic pickers have been developed, but to perform well they often require the tuning of multiple parameters to adapt them to each dataset. Despite the great advance in techniques, some problems remain, such as the difficulty to accurately pick S waves and earthquake recordings with a low signal‐to‐noise ratio. Recently, phase pickers based on deep learning (DL) have shown great potential for event identification and arrival‐time picking. However, the general adoption of these methods for the routine processing of monitoring networks has been held back by factors such as the availability of well‐documented software, computational resources, and a gap in knowledge of these methods. In this study, we evaluate recent available DL pickers for earthquake data, comparing the performance of several neural network architectures. We test the selected pickers using three datasets with different characteristics. We found that the analyzed DL pickers (generalized phase detection, PhaseNet, and EQTransformer) perform well in the three tested cases. They are very efficient at ignoring large‐amplitude transient noise and at picking S waves, a task that is often difficult even for experienced analysts. Nevertheless, the performance of the analyzed DL pickers varies widely in terms of sensitivity and false discovery rate, with some pickers missing a significant percentage of true picks and others producing a large number of false positives. There are also variations in run time between DL pickers, with some of them requiring significant resources to process large datasets. In spite of these drawbacks, we show that DL pickers can be used efficiently to process large seismic datasets and obtain results comparable or better than current standard procedures, The authors gratefully acknowledge the computer resources at Artemisa, funded by the European Union ERDF and Comunitat Valenciana as well as the technical support provided by the Instituto de Física Corpuscular, IFIC (CSIC-UV). Antonio Villaseñor acknowledges funding from Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 grants CGL2017-88864-R, PID2020-114682RB-C31, and the Severo Ochoa Center of Excellence accreditation CEX2019-000928-S to ICM-CSIC

20 pages, 9 figures, 1 table, supporting information https://doi.org/10.1029/2022JB024097.-- Data Availability Statement: Raw seismic waveforms used in this study are available from the IRIS platform (https://ds.iris.edu/ds/nodes/dmc/). Network codes are C1, C, and G. Data preparation and preprocessing were performed using the ObsPy package (Beyreuther et al., 2010). Most of the figures were made with the Generic Mapping Tools (GMT) package (Wessel & Smith, 2006) and the Matplotlib library (Hunter, 2007), In the South-Central Andes, the crustal structures driving the tectonic evolution of the Andean Cordillera remain unresolved. So far, most seismological studies focused on the subduction interface, leaving crustal seismicity and its relationship with crustal deformation and Andean volcanism mostly unconstrained. However, because of their large number compared to higher magnitude events, the characterization of small-magnitude crustal earthquakes is key to identify active structures and better constrain the tectonic models. In this work, we exploit 53 months of continuously recorded, three-component waveforms from the permanent seismic network in central Chile using a deep-learning approach to improve the detection of small-magnitude earthquakes. To increase station coverage, we also use the seismic phases obtained from a previous temporary seismic deployment. We use the obtained seismicity catalog to refine tomographic models of that region, revealing a more detailed architecture of the Chilean forearc. Travel times calculated in the new 3-D velocity model allowed us to locate ∼14,000 earthquakes. Refined double-difference relocations of ∼4,900 events located beneath the West Andean Thrust suggest a large-scale, west-dipping structure which, together with the west-verging tectonic front, likely contributed to the uplift and crustal deformation during the past ∼20 Myr, This research has been supported by the Agencia Nacional de Investigación y Desarrollo (ANID) of Chile (FONDECYT grant N3200633). AV acknowledges the institutional support of the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S)

We study a large and long-lived earthquakes swarm occurring in 2020-2021 in the Bransfield Basin, south of the South Shetland islands, Antarctica. We make use of local seismological stations to det...

Most of the recorded seismicity in central Chile can be linked to the subduction of the Nazca plate. To the east, a much smaller fraction is observed at 0–30 km depths beneath the western Andean thrust. Paleoseismic studies evidenced the occurrence of at least two major earthquakes (M>7) over the past 17 ka, associated with the San Ramón fault (SRF): an important tectonic feature characterizing the west Andean thrust, close the Santiago metropolitan area. To better constrain the crustal seismicity in this area, the Chilean Seismological Center (CSN) extended its permanent seismic network with seven new broadband seismometers deployed around the scarp of the SRF and farther east. The improved azimuthal distribution and reduced station spacing allowed to complete the CSN catalog with more than 900 smaller magnitude earthquakes (ML

Fil: Mackaman Lofland, Chelsea. Jackson School Of Geosciences; Estados Unidos. Department Of Geological Sciences; Estados Unidos

This paper aims to better comprehend the crustal structure of the Precordillera and the Iglesia Valley. Located in the northern sector of the Pampean flat-slab (San Juan, Argentina), this region was the epicenter of the historical 1894, M > 7 earthquake (intensity IX on the modified Mercalli scale) and thus considered as a region of particularly high seismic hazard. The structure and deformation style associated with such events remain poorly understood. In this study, we analyze 4 months of regional seismic records from national and international stations in order to characterize a sequence of 74 crustal events that followed the occurrence of an intermediate magnitude (MW = 4.8 and ML = 5.2) earthquake on October 28th, 2019 for which we constrain the source parameters using regional moment tensor inversion. The analysis also includes the determination of 11 focal mechanisms from P-wave polarities and P–S waves amplitude ratios. Most of the focal mechanisms indicate reverse motion solutions. Seismological results are then integrated with other geophysics (gravity and seismic reflection profiles) as well as geological data, to build a 3D structural model that allows a better understanding of the crustal deformation mechanisms of the study area. Our results suggest that the seismic deformation is mostly concentrated in the basement of the Western Precordillera, at the transition with the Frontal Cordillera. This deformation seems respond to compressional stresses. The proposed model provides evidence of ongoing seismic activity related to the interaction between the thick-skinned deformation of the Frontal Cordillera with the thin-skinned fold and thrust belt of the Western Precordillera.

On 20 January 2019, the Chilean cities of Coquimbo and La Serena were shaken by an intraplate earthquake of Mw 6.7 located at 70 km depth. High peak ground acceleration values and macroseismic intensities were reported. The mainshock was followed by more than 150 aftershocks higher than ML 2.5, a seismic sequence completely recorded by local stations. Using a 3D velocity model, we precisely located the seismicity. The aftershocks were located some 20 km above and shifted from the mainshock but still inside the Nazca plate. We also performed moment tensor inversion of nine events obtaining mostly normal‐fault focal mechanisms and kinematic inversions using the elliptical‐patch approach. We found that the mainshock broke an approximated zone of 6 km by 8 km, propagated upward in the northwest direction and away from the aftershock area. The rupture inverted from accelerograms containing up to 1 Hz was characterized with a high stress drop of 7.51 MPa and a short seismic source time function of only 3 s duration.

In the flat slab region of the South Central Andes (∼31–32◦S), geological observations suggest that the regional crustal structure is inherited from the accretion of different terranes during the Ordovician. These structures were later reactivated, first in extension during the Triassic and later in compression during the Andean uplift since the Miocene. Seismological observations confirmed that those fault structures extend to depth with décollement levels that accommodate current crustal shortening in the region. In order to get better insight on the regional tectonics we computed higher frequency receiver functions (RF) from local slab seismicity of intermediate ∼100 km depth. Using a common conversion point (CCP) stacking method we obtained cross sections showing high vertical resolution crustal structure at the transition between the Precordillera and the Frontal Cordillera. In addition we performed a joint inversion of our high frequency RFs with surface wave data from ambient noise tomography allowing us to constrain absolute seismic wave velocities. Our higher resolution images reveal more structural details down to a depth of 80 km and laterally over the flat slab in good agreement with previous studies. Our results help to better identify very shallow discontinuities in seismic velocities. Recent petrological analyses combined with our high-resolution RF structure correlates with a crustal mafic composition and partial eclogitization in the lower crust. We observe a shift in the crustal structure between the Precordillera (east) and the Frontal Cordillera (west). Regional seismicity and previously determined focal mechanisms superimposed over our images indicate this shifting is a thrust structure extending down to a depth of 40 km. Our results suggest the presence of a master fault between the Cuyania (Western Precordillera) and Chilenia (Frontal Cordillera) terranes that probably accommodates the crustal deformation in the Pampean flat slab region since the Late Ordovician. Fil: Ammirati, Jean Baptiste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Perez Lujan, Sofia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos ; Argentina Fil: Alvarado, Patricia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Beck, Susan. University of Arizona; Estados Unidos Fil: Rocher, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentina Fil: Zandt, George. University of Arizona; Estados Unidos

Universidad de Chile through the Programa Riesgo Sfsmico - Actividades de Interes Nacional (AIN) Agencia Nacional de Investigacion y Desarollo of Chile (ANID) through the Fondo de desarollo Cientffico y tecnico program (FONDECYT) 3200633

In this study, we analyze 100 crustal Precordilleran earthquakes recorded in 2008 and 2009 by 52 broadband seismic stations from the SIEMBRA and ESP, two temporary experiments deployed in the Pampean flat slab region, between the Andean Cordillera and the Sierras Pampeanas in the Argentine Andean backarc region. In order to determine more accurate hypocenters, focal mechanisms and regional stress orientations, we relocated 100 earthquakes using the JHD technique and a local velocity model. The focal depths of our relocated events vary between 6 and 50 km. We estimated local magnitudes between 0.4 ≤ ML ≤ 5.3 and moment magnitudes between 1.3 ≤ Mw ≤ 5.3. Focal mechanisms were determined from new hypocenter relocations and first motion P-wave polarities. Our solutions exhibit a majority of the earthquakes with reverse faulting mechanism. Regional stress tensor from the inversion of P- and T-axis orientations, shows a maximum stress axis (σ1) almost horizontal with a strike of 85° and a minimum stress axis (σ3) almost vertical. We correlate this small-to-moderate magnitude seismicity with the presence of large basement structures beneath the Iglesia-Calingasta Basin in the west and the Eastern Precordillera in the east. The nucleation of deep earthquakes beneath the Iglesia Basin could be related to the presence of a major ramp accommodating the crustal shortening between the Frontal Cordillera and the Precordillera. The crustal seismicity beneath the Precordillera seems to correlate with west-dipping structures rooting deep into the Cuyania basement suggesting a thick-skinned basement deformation system beneath the Precordillera and its shallow thin-skinned fold and thrust belt. Universidad Nacional de San Juan/[Res.100/2008-CEFN]/UNSJ/Argentina Universidad Nacional de San Juan/[PICT2016-0046]/UNSJ/Argentina Universidad Nacional de San Juan/[PICT2017-0676]/UNSJ/Argentina Universidad Nacional de San Juan/[PDTS 80020150600009SJ]/UNSJ/Argentina Universidad Nacional de San Juan/[PROJOVI 10120180400037SJ]/UNSJ/Argentina Universidad Nacional de San Juan/[Res No 1119/18-R-UNSJ]/UNSJ/Argentina UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela Centroamericana de Geología

The eastern Sierras Pampeanas (ESP) are the easternmost expression of a series of foreland uplifts in the Argentine back arc region (~30–34°S) and show spatial and temporal connections with the subduction of the Juan Fernández Ridge (JFR) under the South American plate. In order to get new insights on the mechanisms that control crustal regional tectonics, we computed teleseismic receiver functions (RF) and jointly invert them with Rayleigh-wave phase velocity dispersion curves. RFs allow resolving crustal thickness and intra crustal velocity variations with a good vertical resolution whereas surface wave information helps to constrain absolute seismic wave velocities. Our seismic images have been combined with crustal density modeling in order to further investigate if the shear wave velocity structure obtained from the RF-SW joint inversion could explain the observed gravity variations. Our results show a crustal thickness varying from 35–40 km (east) to 45–50 km (west) with a Moho step at ~66°W. This step regionally presents a NW-SE orientation and is parallel to the trace at the surface of the Valle Fértil–La Huerta (VFLH) lineament (Cuyania-Pampia boundary). Our images also reveal the presence of a high wave velocity (high density) lower crust west of this Moho step, beneath the eastern Sierras Pampeanas (at 66–67°W). This observation suggests the east-dipping extension at depth of the VFLH structure and the underthrusting of the Cuyania lower crust under the Pampia terrane along this structure. Finally, we evidenced localized low velocity zones located at about 10 km beneath late Cenozoic volcanic fields (Pocho, Morro). We believe that these low velocity zones correspond to old magma chambers associated to the recent, slab flattening-related volcanism in the ESP. Fil: Ammirati, Jean Baptiste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Venerdini, Agostina Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina Fil: Alcacer Sanchez, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina Fil: Alvarado, Patricia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina Fil: Miranda, Silvia Alicia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina Fil: Gilbert, Hersh. University of Calgary; Canadá

In the central Andes, the Nazca plate displays large along strike variations in dip with a near horizontal subduction angle between 28 and 32◦S referred to the Pampean flat slab segment. The upper plate above the Pampean flat slab has high rates of crustal seismicity and active basement cored uplifts. The SIEMBRA experiment, a 43-broad-band-seismic-station array was deployed to better characterize the Pampean flat slab region around 31◦S. In this study, we explore the lithospheric structure above the flat slab as a whole and its relation toseismicity. We use the SIEMBRA data to perform a joint inversion of teleseismic receiver functions and Rayleigh wave phase velocity dispersion to constrain the shear wave velocity variations in the lithosphere. Our joint inversion results show: (1) the presence of several upper-plate mid-crustal discontinuities and their lateral extent that are probably related to the terrane accretion history; (2) zones of high shear wave velocity in the upper-plate lower crust associated with a weak Moho signal consistent with the hypothesis of partial eclogitization in the lower crust; (3) the presence of low shear-wave velocities at ∼100 km depth interpreted as the subducting oceanic crust. Finally, in order to investigate the relation of the lithospheric structure to seismicity, we determine an optimal velocity?depth model based on the jointinversion results and use it to perform regional moment tensor inversions (SMTI) of crustal and slab earthquakes. The SMTI for 18 earthquakes that occurred between 2007 and 2009 in the flat slab region below Argentina, indicates systematically shallower focal depths for slab earthquakes (compared with inversions using previous velocity models). This suggests that the slab seismicity is concentrated mostly between 90 and 110 km depths within thesubducting Nazca plate?s oceanic crust and likely related to dehydration. In addition, the slab earthquakes exhibit extensional focal mechanisms suggesting new faulting at the edges of the flat portion of the slab. SMTI solutions for upper-plate crustal earthquakes match well the geological observations of reactivated structures and agree with crustal shortening. Our new constraints on flat slab structure can aid earthquake characterization for regional seismichazard assessment and efforts to help understand the mechanisms for slab flattening in the central Andes. Fil: Ammirati, Jean Baptiste. Ministerio de Ciencia, Tecnología e Innovación Productiva. Agencia Nacional de Promoción Cientifíca y Tecnológica; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina Fil: Alvarado, Patricia Monica. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Beck, Susan. Arizona State University; Estados Unidos

Elastic properties in twelve representative rock samples from Central and Western Precordillera in the Andean backarc region of Argentina between 30 and 31S were estimated from detailed petrological analysis. Thus, P and S seismic-wave velocities (Vp, Vs) as well as Poisson´s ratio (s) among other parameterswere derived for gabbros, leuco-gabbros and wehrlites, in greenschist and amphibolite metamorphic conditions using a framework of a wide variety of empirical observations from active continental margins. In addition, Vs lithosphere models along two westeeast cross sections were obtainedusing a joint inversion of teleseismic Rayleigh waves and receiver functions. These models clearly delineate the upper-plate crustal structure and the flat-slab subduction of the Nazca plate at about 100 km depth in this region. The suggested seismic velocity structure shows a relatively low (

This paper is a contribution to the knowledge of the crustal structure of the eastern flank of the Valle Fértil - La Huerta ranges (Western Sierras Pampeanas, San Juan, Argentina) at 31°S, in the Andean foreland region, where the Nazca plate is subducting horizontally at about 100 km depth. A 1D velocity model was constrained, combining petrographic and seismological observations from analysis of 19 igneous and metaigneous plutonic rocks belonging to the Famatinian (Ordovician) magmatic arc, which make up most of the crystalline basement of these ranges. Granitoid lithologies predominate in the northern region whereas mafic lithologies are more common to the south. The seismological analysis consisted of modeling teleseismic receiver functions near three seismological stations: LUNA, MAJA and CHUC, in places where those rocks are dominant. Thus, P and S seismic-wave velocities (Vp and Vs) and Poisson´s coefficient (ν), among other elastic parameters, were obtained. The seismic velocity model indicates an overthickened crust with an average thickness between 55 and 60 km, which matches with global average values (~41km); this agrees well with the hypothesis of partial eclogitization in the lower crust. The presence of two seismic velocity discontinuities at mid-crustal levels (12 and 28 km depths), likely associated to décollements, might be related to the accretion of the Cuyania terrane to the Pampia terrane. We obtained low P seismic-wave velocities (Vp ~5.8 km/s), Vp/Vs ratio (~1.70) in upper crust levels consistent with granitoid lithologies, as well as high P seismic-wave velocities (Vp ~6.76 km/s), Vp/Vs ratio (~1.78) in lower crust levels; these figures match with mafic lithologies of a more dense (~3.00 g/cm3), lower crust with respect to other back-arc Andean regions. Also, these values are consistent with the existence of mafic rocks composed of olivine, ortho- and clinopyroxene, which constitute the root of the Famatinian magmatic arc. These results indicate high-grade metamorphic conditions and depths corresponding to geophysical properties of middle to lower crust and correlate with the hypothesis of a dehydrated, cool and magnesium-enriched mantle located in the region between the subducted Nazca slab and the bottom of the Cuyania terrain crust.

The subduction of the Nazca plate under the South American plate around 31°S is characterized by flat slab geometry. The (Chilean) Pampean flat slab of Argentina associated with the subduction of the Juan Fernandez ridge lies in a region of a series of foreland uplifts corresponding to the thin-skinned Precordillera and basement cored Sierras Pampeanas ranges. The SIEMBRA project deployed 40 broadband stations in 2008?2009 in both the Precordillera and the Sierras Pampeanas with the aim to foster the understanding of the entire central Andean flat slab region. One of the SIEMBRA station (DOCA) located on the western flank of Sierra de la Invernada in the Central Precordillera appears particularly appropriate to study the crustal structure and eventually detect discontinuities related to terranes establishment. We thus performed a receiver function analysis using teleseismic data recorded at the DOCA station during the SIEMBRA project and from October 2011 to June 2012 using a broadband UNSJ (National University of San Juan) seismic station with the purpose to obtain crustal images with details of the intracrustal structure consistent with a mechanism that could explains both the observed earthquake depths and the uplift pattern in the Central Precordillera. Our results show that the Moho beneath the Precordillera lies at a depth of about 66 km. The Moho signal appears diminished and behaves irregularly as a function of azimuthal orientations. Although this observation could be the result of an irregular geometry it also correlates with the hypothesis of partial eclogitisation in the lower crust. Two mid-crustal discontinuities have also been revealed. The shallower one could correspond to a décollement level between the Precordilleran strata and the Cuyania basement at 21 km depth. The deeper one which the presence has been matched with a sharp decrease of the crustal seismic activity drove us to the hypothesis of a major change in crustal composition at 36 km. Finally the flat portion of the subducted slab has been imaged lying at about 100 km depth. Fil: Ammirati, Jean Baptiste. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Ministerio de Ciencia. Tecnología e Innovación Productiva. Agencia Nacional de Promoción Cientifíca y Tecnológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Alvarado, Patricia Monica. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Perarnau, Marcelo Andres. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Saez, Mauro. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Monsalvo Ciancio, Victor Guillermo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Ciencia. Tecnología e Innovación Productiva. Agencia Nacional de Promoción Cientifíca y Tecnológica; Argentina