Constructing forearc architecture over megathrust seismic cycles: Geological snapshots from the Maule earthquake region, Chile

Aron, Felipe; Cembrano, José; Astudillo, Felipe; Allmendinger, Richard W.; Arancibia, Gloria

doi:10.1130/b31125.1

Cited by 24 publications

(23 citation statements)

References 46 publications

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“…(b) Cross-section along profile P01 shows the best source depth estimated in this study. Brown line is the top of the oceanic subducting slab, purple dashed line is the Moho discontinuity, blue solid line is the bathymetry obtained from the 2-D velocity-depth model of Zelt (1999). accumulates over repeated subduction seismic cycles and leads to large tensional earthquakes as was the case for the Pichilemu event off Maule (Farías et al 2011;Ruiz et al 2014;Aron et al 2014). Similar extension in the forearc following a megathrust earthquake has been reported for the cases of the 1960 south Chile (Plafker 1967) and Tohoku megathrust earthquakes (e.g.…”

Section: Interplay Between Continental Crustal Faults and Intraplate mentioning

confidence: 99%

Structure and tectonics of the central Chilean margin (31°–33°S): implications for subduction erosion and shallow crustal seismicity

Contreras‐Reyes¹,

Ruiz²,

Becerra³

et al. 2015

Geophys. J. Int.

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S U M M A R YThe pre-and current collision of the Juan Fernández Ridge with the central Chilean margin at 31• -33• S is characterized by large-scale crustal thinning and long-term subsidence of the submarine forearc caused by subduction erosion processes. Here, we study the structure of the central Chilean margin in the ridge-trench collision zone by using wide-angle and multichannel seismic data. The transition from the upper to middle continental slope is defined by a trenchward dipping normal scarp with variable offsets of 500-2000 m height. Beneath the scarp, the 2-D velocity-depth models show a prominent lateral velocity contrast of >1 s −1 that propagates deep into the continental crust defining a major lateral seismic discontinuity. The discontinuity is interpreted as the lithological contact between the subsided/collapsed outermost forearc (composed of eroded and highly fractured volcanic rocks) and the seaward part of the uplifted Coastal Cordillera (made of less fractured metamorphic/igneous rocks). Extensional faults are abundant in the collapsed outermost forearc, however, landward of the continental slope scarp, both extensional and compressional structures are observed along the uplifted continental shelf that forms part of the Coastal Cordillera. Particularly, at the landward flank of the Valparaíso Forearc Basin (32• -33.5• S), shallow crustal seismicity has been recorded in 2008-2009 forming a dense cluster of thrust events of M w 4-5. The estimated hypocentres spatially correlate with the location of the fault scarp, and they highlight the upper part of the seismic crustal discontinuity.

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Section: Interplay Between Continental Crustal Faults and Intraplate mentioning

confidence: 99%

Structure and tectonics of the central Chilean margin (31°–33°S): implications for subduction erosion and shallow crustal seismicity

Contreras‐Reyes¹,

Ruiz²,

Becerra³

et al. 2015

Geophys. J. Int.

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“…In north Chile, surface cracks are clearly related to large earthquakes (Delouis et al, ; Loveless et al, ; Scott et al, ). Young surface cracks are also found above the northern end of the Maule 2010 slip area (Aron et al, ; Arriagada et al, ) where normal faults are long‐lived features (Aron et al, ). Young surface cracks were identified above the downdip end of the Tohoku 2011 finite fault (Mizoguchi et al, ).…”

Section: Comparison With Observationsmentioning

confidence: 99%

“…The plate boundary segment involved in the 2010 M w = 8.8 Maule (Chile) event was previously active in 1835 (Darwin, ). Aron et al () estimate a recurrence range of 84–178 years for the megathrust cycle. The long‐term Maxwell time ranges between 5 and 70 years (Ding & Lin, ; Piersanti, ).…”

Section: Numerical Modelmentioning

confidence: 99%

The Geodetic Signature of the Earthquake Cycle at Subduction Zones: Model Constraints on the Deep Processes

Govers

Furlong

Wiel

et al. 2018

Reviews of Geophysics

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Recent megathrust events in Tohoku (Japan), Maule (Chile), and Sumatra (Indonesia) were well recorded. Much has been learned about the dominant physical processes in megathrust zones: (partial) locking of the plate interface, detailed coseismic slip, relocking, afterslip, viscoelastic mantle relaxation, and interseismic loading. These and older observations show complex spatial and temporal patterns in crustal deformation and displacement, and significant differences among different margins. A key question is whether these differences reflect variations in the underlying processes, like differences in locking, or the margin geometry, or whether they are a consequence of the stage in the earthquake cycle of the margin. Quantitative models can connect these plate boundary processes to surficial and far‐field observations. We use relatively simple, cyclic geodynamic models to isolate the first‐order geodetic signature of the megathrust cycle. Coseismic and subsequent slip on the subduction interface is dynamically (and consistently) driven. A review of global preseismic, coseismic, and postseismic geodetic observations, and of their fit to the model predictions, indicates that similar physical processes are active at different margins. Most of the observed variability between the individual margins appears to be controlled by their different stages in the earthquake cycle. The modeling results also provide a possible explanation for observations of tensile faulting aftershocks and tensile cracking of the overriding plate, which are puzzling in the context of convergence/compression. From the inversion of our synthetic GNSS velocities we find that geodetic observations may incorrectly suggest weak locking of some margins, for example, the west Aleutian margin.

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“…ATFs also have been thought to control the Neogene forearc basin architecture and megathrust rupture segmentation associated with the seismic subduction cycle (Glodny et al, ; Melnick et al, ). Furthermore, deformation of the ATFs might be activated from megathrust earthquakes (Aron et al, ; Arriagada et al, ; Farías et al, ; Stanton‐Yonge et al, ), and may control crustal fluid migration within the intra‐arc region (Cembrano & Lara, ; Katz, ; Pérez‐Flores et al, ; Rivera & Cembrano, ; Roquer et al, ; Sánchez‐Alfaro et al, ; Sielfeld et al, ; Wrage et al, ).…”

Section: Tectonic Setting Of Southern Andesmentioning

confidence: 99%

“…In the Andean Southern Volcanic Zone (SVZ), in particular along the margin‐parallel Liquiñe‐Ofqui Fault System (LOFS), stratovolcanoes, minor eruptive centers, and geothermal features, are spatially related to the geometry and kinematics of long‐lived faults (Cembrano & Lara, ; Sánchez‐Alfaro et al, ). Additionally, for the long‐term geological record, margin‐parallel faults (i.e., LOFS) coexist with second order transverse‐to‐the‐arc oriented faults (Andean Transverse Faults, ATF; Aron et al, ; Kaizuka, ; Katz, ; Melnick et al, ; Yáñez et al, ; among others), developing a causal relationship with crustal fluid‐flow (Cembrano & Lara, ; Pérez‐Flores et al, , ; Sánchez‐Alfaro et al, ; Tardani et al, ; Wrage et al, ). Based on kinematic and dynamic analysis of fault‐slip data, Pérez‐Flores et al () suggest that bulk transpressional deformation is partially partitioned into variable orientations and scales within the Southern Volcanic Zone (SVZ) of the Andean magmatic arc.…”

Section: Introductionmentioning

confidence: 99%

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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Constructing forearc architecture over megathrust seismic cycles: Geological snapshots from the Maule earthquake region, Chile

Cited by 24 publications

References 46 publications

Structure and tectonics of the central Chilean margin (31°–33°S): implications for subduction erosion and shallow crustal seismicity

Structure and tectonics of the central Chilean margin (31°–33°S): implications for subduction erosion and shallow crustal seismicity

The Geodetic Signature of the Earthquake Cycle at Subduction Zones: Model Constraints on the Deep Processes

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

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