Seismogenic zone high permeability in the Central Andes inferred from relocations of micro-earthquakes

Nippress, S.; Rietbrock, Andreas

doi:10.1016/j.epsl.2007.08.032

Cited by 41 publications

(27 citation statements)

References 33 publications

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“…The shallower downdip region under the MP could be interpreted as a shallower seismogenic zone (Schurr et al, 2012). This pattern in the distribution of seismicity was also observed in the aftershocks of the Antofagasta and Tocopilla earthquakes around the MP (Nippress & Rietbrock, 2007;Schurr et al, 2012) and in the seismicity recorded by the IPOC network (Sippl et al, 2018). Therefore, this seismic gap is a persistent feature lasting at least since the start of the seismic record.…”

Section: Interplate Seismicitymentioning

confidence: 59%

Fluids Along the Plate Interface Influencing the Frictional Regime of the Chilean Subduction Zone, Northern Chile

Pastén-Araya

Salazar

Ruiz

et al. 2018

Geophysical Research Letters

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The plate interface beneath the Mejillones Peninsula in Northern Chile is characterized by anomalous seismogenic behaviors, with seismic and aseismic slip, and low coupling values. We analyze this zone through the seismicity pattern and a 3-D tomography model. We identify high V P /V S values within the oceanic crust and in the lower continental crust, which we interpret as hydrated zones rich in fluids. These zones are correlated with the Mejillones fracture zone and with highly permeable lithologies of the lower continental crust, which allow a greater accumulation of fluids at the plate interface beneath the Mejillones Peninsula. Additionally, these areas exhibit a high rate of seismicity and concentrated swarms and repeaters. We propose that the presence of fluids controls the anomalous seismogenic behavior along the plate interface beneath the Mejillones Peninsula.Plain Language Summary The interplate zone beneath Mejillones Peninsula (MP), northern Chile, presents an anomalous seismogenic behavior with aseismic pulses, low coupling values, and acting as a seismic barrier for earthquakes occurred in adjacent areas. We believe that this anomalous behavior is due to the presence of fluids in the interplate zone under the MP. To corroborate this, we study the seismicity recorded by a local seismological network and constructed a tomographic velocity model. Our results show that within the oceanic crust and in the lower continental crust exist the presence of fluids that concentrates to the north and center of the MP, which correlate with the presence of the Mejillones fracture zone and with more fractured and permeable lithologies of the continental crust. This situation changes to the south of the MP where fluid concentration is lower. This is the first detailed attempt to characterize the role of fluids in the rheology of barriers within subduction zones and to distinguish geological controls on the fluid distribution. We believe that this type of study is fundamental for facilitating future prospective analysis of earthquake distributions and conducting hazard assessments.

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Section: Interplate Seismicitymentioning

confidence: 59%

Fluids Along the Plate Interface Influencing the Frictional Regime of the Chilean Subduction Zone, Northern Chile

Pastén-Araya

Salazar

Ruiz

et al. 2018

Geophysical Research Letters

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“…Smaller magnitude aftershocks (M < 4) occur predominantly in areas of larger co-seismic slip, and are more loosely distributed laterally and in depth. Consequently, they might be associated with processes in the damage zone surrounding the megathrust plate interface, and could be triggered by coseismically-released fluids [e.g., Nippress and Rietbrock, 2007].…”

Section: Resultsmentioning

confidence: 99%

Seismic‐afterslip characterization of the 2010 M_W 8.8 Maule, Chile, earthquake based on moment tensor inversion

Agurto

Rietbrock

Ryder

et al. 2012

Geophysical Research Letters

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On February 27th 2010, a MW8.8 earthquake struck the coast of south‐central Chile, rupturing ∼500 km along the subduction interface. Here we estimate the amount of seismically‐released afterslip (SRA) and the mechanisms underlying the distribution of aftershocks of this megathrust earthquake. We employ data from a temporary local network to perform regional moment tensor (RMT) inversions. Additionally, we relocate global centroid‐moment‐tensor (GCMT) solutions, assembling a unified catalog covering the time period from the mainshock to March 2012. We find that most (70%) of the aftershocks with MW> 4 correspond to thrust events occurring on the megathrust plane, in areas of moderate co‐seismic slip between 0.15 and 0.7 fraction of the maximum slip (Smax). In particular, a concentration of aftershocks is observed between the main patches of co‐seismic slip, where the highest values of SRA are observed (1.7 m). On the other hand, small events, MW< 4, occur in the areas of largest co‐seismic slip (>0.85 Smax), likely related to processes in the damage zone surrounding the megathrust plane. Our study provides insight into the mechanics of the seismic afterslip pattern of this large megathrust earthquake and a quantitative approach to the distribution of aftershocks relative to coseismic slip that can be used for similar studies in other tectonic settings.

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“…In fact, pseudotachylytes are rarely found in sediments, although several authors have reported pseudotachylytes from other ancient exposed subduction mélanges [ Ikesawa et al , 2003; Kitamura et al , 2005; Rowe et al , 2005]. Relocation of seismicity at convergent margins as resolved by local networks [e.g., Nippress and Rietbrock , 2007] yields a narrow zone of aftershock activity that embraces the entire plate interface zone, from the base of the upper plate across the subduction channel to the top of the downgoing plate, clearly indicating that sediment‐dominated subduction shear zones sustain seismic rupture. The general scarcity of pseudotachylytes in sediments and mélanges is usually attributed to the hydraulic state that may serve to reduce effective stresses allowing less heat generation on rupture surfaces, as well as providing an efficient medium for heat dissipation, etc.…”

Section: Discussionmentioning

confidence: 99%

Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone

et al. 2009

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[1] We present observations from a continuous exposure of an ancient plate interface in the depth range of its former seismogenic zone in the central Alps of Europe related to Late Cretaceous-early Tertiary subduction and accretion of the South Penninic lower plate underneath the Adriatic upper plate. The material forming the exposed plate interface zone has experienced flow and fracturing over an extended period of time followed by syncollisional exhumation, thus reflecting a multistage evolution. Fabric formation and metamorphism, however, chiefly record the deformation conditions of the precollisional setting along the plate interface. We identify an unstable slip domain from pseudotachylytes occurring in the temperature range between 200 and 300°C. This zone coincides with a domain of intense veining in the subduction mélange with mineral growth into open cavities, indicating fast, possibly seismic, rupture. Evidence for transient near-lithostatic fluid pressure as well as brittle fractures competing with mylonitic shear zones continues into the region below the occurrence of pseudotachylytes, possibly reflecting a zone of conditionally stable slip. The zone above the unstable slip area is devoid of veins but displays ample evidence of fluid-assisted processes similar to the deeper zone: solution-precipitation creep and dehydration reactions in the mélange matrix, hydration, and sealing of the base of the upper plate. Seismic rupture here is possibly expressed by ubiquitous localized deformation zones. We hypothesize that trenchward sealing of parts of the plate interface as well as reaction-enhanced destruction of upper plate permeability is an important component, localizing the unstable slip zone. This relation may result from the competition of the pervasive, presumably interseismic, pressure solution creep destroying permeability and building elevated fluid pressure until the strength threshold is reached with seismic failure.Citation: Bachmann, R., O. Oncken, J. Glodny, W. Seifert, V. Georgieva, and M. Sudo (2009), Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone,

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Seismogenic zone high permeability in the Central Andes inferred from relocations of micro-earthquakes

Cited by 41 publications

References 33 publications

Fluids Along the Plate Interface Influencing the Frictional Regime of the Chilean Subduction Zone, Northern Chile

Fluids Along the Plate Interface Influencing the Frictional Regime of the Chilean Subduction Zone, Northern Chile

Seismic‐afterslip characterization of the 2010 M_W 8.8 Maule, Chile, earthquake based on moment tensor inversion

Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone

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Seismogenic zone high permeability in the Central Andes inferred from relocations of micro-earthquakes

Cited by 41 publications

References 33 publications

Fluids Along the Plate Interface Influencing the Frictional Regime of the Chilean Subduction Zone, Northern Chile

Fluids Along the Plate Interface Influencing the Frictional Regime of the Chilean Subduction Zone, Northern Chile

Seismic‐afterslip characterization of the 2010 MW 8.8 Maule, Chile, earthquake based on moment tensor inversion

Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone

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Seismic‐afterslip characterization of the 2010 M_W 8.8 Maule, Chile, earthquake based on moment tensor inversion