Change in the pattern of crustal seismicity at the Southern Central Andes from a local seismic network

Nacif, Silvina; Lupari, Marianela; Triep, Enrique G.; Nacif, Andrés; Álvarez, Orlando; Folguera, Andrés; Giménez, Mario

doi:10.1016/j.tecto.2017.04.012

Cited by 9 publications

(12 citation statements)

References 53 publications

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“…The trends in the modeled lateral variability of integrated lithospheric strength found in our study (Figures 5a‐5b) can be qualitatively compared with previous elastic thickness estimates (Te), derived from a cross‐correlation between topography and Bouguer gravity anomaly (Astort et al., 2019; Ibarra & Prezzi, 2019; Nacif et al., 2017; Sánchez et al., 2018; Tassara & Yáñez, 2003). High values of Te usually are indicative of a strong lithosphere, whereas low values of Te correspond to a weaker lithosphere (e.g., Burov, 2011; Burov & Diament, 1995; Watts & Burov, 2003).…”

Section: Discussionsupporting

confidence: 86%

“…Previous studies on upper‐plate earthquakes (e.g., SIEMBRA, ESP, CHARGE, CHARSME, and CHASE seismic experiments; Alvarado et al., 2005; Alvarado, Pardo, et al., 2009; Marot et al., 2014; Nacif et al., 2013, 2017; Olivar et al., 2018; Rivas et al., 2019; Venerdini et al., 2020) have depicted an heterogeneous earthquake distribution with seismic activity decreasing toward the south of the flat subduction segment, though such low seismicity rates could be partly attributed to a poorer coverage of seismic networks in the steep segment of the slab. A major outcome from these previous studies was to correlate monitored seismicity to localized weakening within neotectonic fault areas, either linked to Cenozoic structures or to compressional reactivation of inherited structures and fabrics (e.g., Astini et al., 1995; Azcuy & Caminos, 1987; Giambiagi et al., 2003; Jordan et al., 1983; Kay et al., 2006; Llambias et al., 1993; Llambias & Sato, 1990; Mpodozis & Kay, 1990; Ramos, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…The SCA are one of the most seismically active regions along the South American convergent margin, where past seismic events had devastating impacts on humans, with loss of life and far‐reaching economic repercussions (Alvarado & Beck, 2006; Alvarado, Barrientos, et al., 2009; Ammirati et al., 2019; Gregori & Christiansen, 2018; Ruiz & Madariaga, 2018). So far, seismological research in the SCA focused on understanding the causative dynamics of the recorded seismicity within the oceanic plate and along the subduction interface (e.g., Anderson et al., 2007; Cloos & Shreve, 1996; Hackney et al., 2006; Linkimer et al., 2020; Moreno et al., 2010, 2014; Wagner et al., 2020; Weiss et al., 2019), while less attention has been paid to the mechanisms controlling upper‐plate seismicity (Alvarado et al., 2005; Alvarado, Barrientos, et al., 2009; Alvarado, Pardo, et al., 2009; Ammirati et al., 2019; Nacif et al., 2017; Smalley & Isacks, 1990; Smalley et al., 1993).…”

Section: Introductionmentioning

confidence: 99%

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Long‐Term Lithospheric Strength and Upper‐Plate Seismicity in the Southern Central Andes, 29°–39°S

Piceda

Scheck‐Wenderoth

Cacace

et al. 2022

Geochem Geophys Geosyst

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We examined the relationship between the mechanical strength of the lithosphere and the distribution of seismicity within the overriding continental plate of the southern Central Andes (SCA, 29°–39°S), where the oceanic Nazca Plate changes its subduction angle between 33°S and 35°S, from subhorizontal in the north (<5°) to steep in the south (∼30°). We computed the long‐term lithospheric strength based on an existing 3D model describing variations in thickness, density, and temperature of the main geological units forming the lithosphere of the SCA and adjacent forearc and foreland regions. The comparison between our results and seismicity within the overriding plate (upper‐plate seismicity) shows that most of the events occur within the modeled brittle domain of the lithosphere. The depth where the deformation mode switches from brittle frictional to thermally activated ductile creep provides a conservative lower bound to the seismogenic zone in the overriding plate of the study area. We also found that the majority of upper‐plate earthquakes occurs within the realm of first‐order contrasts in integrated strength (12.7–13.3 log Pam in the Andean orogen vs. 13.5–13.9 log Pam in the forearc and the foreland). Specific conditions characterize the mechanically strong northern foreland of the Andes, where seismicity is likely explained by the effects of slab steepening.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long‐Term Lithospheric Strength and Upper‐Plate Seismicity in the Southern Central Andes, 29°–39°S

Piceda

Scheck‐Wenderoth

Cacace

et al. 2022

Geochem Geophys Geosyst

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“…Long‐term geologic data show that continental margin high‐strain domains are mostly localized along the Miocene‐Present day volcanic arc and/or at long‐lived ATF (e.g., Cembrano & Lara, ; Glodny et al, ; Pérez‐Flores et al, ; Rosenau et al, ; among others). If the current strain rate is indeed higher in the volcanic arc domain, the SLB should be deeper than that of the forearc and foreland regions given a constant geothermal gradient, which is something not supported by our data and that of previous work (e.g., Nacif et al, ; Salazar et al, ). Therefore, although strain rate in the volcanic arc is higher, the effect of heat flux and associated higher geothermal gradient largely overcomes that of strain rate.…”

Section: Discussioncontrasting

confidence: 85%

“…The latter, down to ~60 km depth in the forearc‐slab boundary, progressively shallows up to ~15 km beneath the active volcanic front, describing a convex geometry in line with the maximum depth of crustal events. In turn, in the southern Central Andes (32–33.4°S), Nacif et al () show similar hypocentral depths beneath the volcanic front (<12 km). Integrating EHB Bulletin Catalog data, this author indicates also how foreland/back‐arc seismic activity locates progressively deeper to the east, down to reach the continental Moho (~ 50 km depth), about ~550 km away from the trench.…”

Section: Discussionmentioning

confidence: 84%

Intra‐Arc Crustal Seismicity: Seismotectonic Implications for the Southern Andes Volcanic Zone, Chile

2019

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We examine the intra-arc crustal seismicity of the Andean Southern Volcanic Zone. Our aim is to resolve interseismic deformation in an active magmatic arc dominated by both margin-parallel (Liquiñe-Ofqui fault system, LOFS) and Andean transverse faults. Crustal seismicity provides information about the schizosphere tectonic state, delineating the geometry and kinematics of high strain domains driven by oblique-subduction. Here, we present local seismicity based on 16-month data collected from 34 seismometers monitoring a~200-km-long section of the Southern Volcanic Zone, including the Lonquimay and Villarrica volcanoes. We located 356 crustal events with magnitudes between M w 0.6 and M w 3.6. Local seismicity occurs at depths down to 40 km in the forearc and consistently shallower than 12 km beneath the volcanic chain, suggesting a convex shape of the crustal seismogenic layer bottom. Focal mechanisms indicate strike-slip faulting consistent with ENE-WSW shortening in line with the long-term deformation history revealed by structural geology studies. However, we find regional to local-scale variations in the shortening axes orientation as revealed by the nature and spatial distribution of microseismicity, within three distinctive latitudinal domains. In the northernmost domain, seismicity is consistent with splay faulting at the northern termination of the LOFS; in the central domain, seismicity distributes along ENE-and WNW-striking discrete faults, spatially associated with, hitherto seismic Andean transverse faults. The southernmost domain, in turn, is characterized by activity focused along a N15°E striking master branch of the LOFS. These observations indicate a complex strain compartmentalization pattern within the intra-arc crust, where variable strike-slip faulting dominates over dip-slip movements.Plain Language Summary In active volcanic chains, there is a strong interplay between deformation and volcanism. In this research, we take the "pulse" of active tectonics in a volcanic arc setting by measuring natural seismicity. We installed a network of 34 seismometers over 200 km along the volcanic arc in Southcentral Chile. Our results indicate active faulting in coherence with long-lived faults and the overall regional-scale stress regime. In fact, crustal regions in which faults are more active are spatially associated with inherited faults and with higher temperature gradient domains, as inferred from volcanic and geothermal activity. The maximum depth of seismicity is shallow (<12 km) in the central part of the volcanic arc, whereas is much deeper (~40 km) toward the forearc and back-arc regions. This observation suggests that elevated geothermal gradients lead to a thinner brittle portion of crust, which is then mechanically easier to (re-)break up. Our results can be used for understanding the way by which faulting interacts with crustal fluids, which in turn may help improving geothermal exploration strategies and seismic hazard assessment. Furthermore, seismicity reveals detailed information on how...

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Quaternary Deformation in the Neuquén Basin, Explained by the Interaction Between Mantle Dynamics and Tectonics

Sagripanti

Colavitto

Astort

et al. 2020

Springer Earth System Sciences

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Change in the pattern of crustal seismicity at the Southern Central Andes from a local seismic network

Cited by 9 publications

References 53 publications

Long‐Term Lithospheric Strength and Upper‐Plate Seismicity in the Southern Central Andes, 29°–39°S

Long‐Term Lithospheric Strength and Upper‐Plate Seismicity in the Southern Central Andes, 29°–39°S

Intra‐Arc Crustal Seismicity: Seismotectonic Implications for the Southern Andes Volcanic Zone, Chile

Quaternary Deformation in the Neuquén Basin, Explained by the Interaction Between Mantle Dynamics and Tectonics

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