Crustal thickness and mantle wedge structure from receiver functions in the Chilean Maule region at 35°S

Dannowski, Anke; Grevemeyer, Ingo; Kraft, Helene Anja; Arroyo, Ivonne G.; Thorwart, Martin

doi:10.1016/j.tecto.2013.02.015

Cited by 11 publications

(13 citation statements)

References 25 publications

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“…A similar clustering of aftershocks in two depth levels downdip of the coseismic rupture was first observed in the wake of the M w 8.8 Maule earthquake (Lange et al 2012) suggesting that the band of deep seismicity could be a general pattern for the Central Chilean subduction zone. For the Maule 2010 and the Illapel 2015 earthquakes, the depth of the aseismic region between the upper and the lower cluster roughly coincides with the depth of the continental Moho from receiver function analysis (Gilbert et al 2006;Dannowski et al 2013). However, beyond this observation of spatial correlation with the continental Moho, the physical processes that govern the separation of seismicity into two depth levels remains enigmatic.…”

Section: R E S U Lt S a N D Discussionmentioning

confidence: 84%

Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

Lange

Geersen

Barrientos

et al. 2016

Geophysical Journal International

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Powerful subduction zone earthquakes rupture thousands of square kilometres along continental margins but at certain locations earthquake rupture terminates. To date, detailed knowledge of the parameters that govern seismic rupture and aftershocks is still incomplete. On 2015 September 16, the Mw 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here, we analyse the temporal and spatial pattern of the coseismic rupture and aftershocks in relation to the tectonic setting in the earthquake area. Aftershocks cluster around the area of maximum coseismic slip, in particular in lateral and downdip direction. During the first 24 hr after the main shock, aftershocks migrated in both lateral directions with velocities of approximately 2.5 and 5 km hr−1. At the southern rupture boundary, aftershocks cluster around individual subducted seamounts that are related to the downthrusting Juan Fernández Ridge. In the northern part of the rupture area, aftershocks separate into an upper cluster (above 25 km depth) and a lower cluster (below 35 km depth). This dual seismic–aseismic transition in downdip direction is also observed in the interseismic period suggesting that it may represent a persistent feature for the Central Chilean subduction zone.

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Section: R E S U Lt S a N D Discussionmentioning

confidence: 84%

Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

Lange

Geersen

Barrientos

et al. 2016

Geophysical Journal International

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“…Thus, if the subduction zone is colder than predicted in these scenarios (e.g., less frictional heating and/or greater hydrothermal cooling), the downdip limit of the seismogenic zone may be controlled by the change in frictional properties of the upper plate at the continental Moho [e.g., Hyndman and Peacock , ]. For the 2010 Mw 8.8 Maule earthquake, coseismic slip extended from ~34°S to ~38°S at depths of ~25–40 km [e.g., Lorito et al ., ]; this rupture area is primarily updip of intersection between the plate interface and the continental Moho (at ~38 km depth) [ Dannowski et al ., ]. However, aftershocks of the Maule earthquake extend downdip to 50 km depth on the plate interface [ Lange et al ., ], below the continental Moho.…”

Section: Discussionmentioning

confidence: 99%

Remarkably consistent thermal state of the south central Chile subduction zone from 36°S to 45°S

Rotman

Spinelli

2014

JGR Solid Earth

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Delineating rupture areas of subduction zone earthquakes is necessary for understanding the controls on seismic and aseismic slip. For the largest recorded earthquake, the 1960 Chile event with moment magnitude 9.5, the rupture area is only loosely defined due to limitations in the global seismic network at the time. The rupture extends~900 km along strike. Coastal deformation is consistent with either a constant rupture width of~180-200 km along the entire length or a narrower (~115 km) rupture in the southern half. A southward narrowing of the seismogenic zone has been hypothesized to result from warming of the subduction zone to the south, where the subducting plate is younger. We present results of thermal models at 36°S, 38°S, 43°S, and 45°S to examine potential along-strike changes in thermal state. Models most consistent with observed surface heat flux include fluid circulation in the oceanic crust that advects heat to the ocean. This ventilated hydrothermal circulation preferentially cools transects with young subducting lithosphere; frictional heating preferentially warms transects with older subducting lithosphere. The combined effects of frictional heating and hydrothermal circulation increase décollement temperatures in the 36°S and 38°S transects by up to~155°C and decrease temperatures in the 45°S transect by up to~150°C. In our preferred models, décollement temperatures 200 km landward of the trench in all four transects arẽ 350-400°C. This is consistent with a constant~200 km wide seismogenic zone for the 1960 M w 9.5 rupture, with decreasing slip magnitude in the southern half of the rupture.

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“…DeMets et al, 2010). Large earthquake ruptures along the margin tend to occur within highly coupled segments (Métois et al, 2012).…”

Section: Characteristics Of the Central Chile Subduction Zonementioning

confidence: 99%

Anatomy of a megathrust: The 2010 M8.8 Maule, Chile earthquake rupture zone imaged using seismic tomography

Hicks

Rietbrock

Ryder

et al. 2014

Earth and Planetary Science Letters

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Knowledge of seismic velocities in the seismogenic part of subduction zones can reveal how material properties may influence large ruptures. Observations of aftershocks that followed the 2010 M w 8.8 Maule, Chile earthquake provide an exceptional dataset to examine the physical properties of a megathrust rupture zone. We manually analysed aftershocks from onshore seismic stations and ocean bottom seismometers to derive a 3-D velocity model of the rupture zone using local earthquake tomography. From the trench to the magmatic arc, our velocity model illuminates the main features within the subduction zone. We interpret an east-dipping high P-wave velocity anomaly (>6.9 km/s) as the subducting oceanic crust and a low P-wave velocity (<6.25 km/s) in the marine forearc as the accretionary complex. We find two large P-wave velocity anomalies (∼7.8 km/s) beneath the coastline. These velocities indicate an ultramafic composition, possibly related to extension and a mantle upwelling during the Triassic. We assess the role played by physical heterogeneity in governing megathrust behaviour. Greatest slip during the Maule earthquake occurred in areas of moderate P-wave velocity (6.5-7.5 km/s), where the interface is structurally more uniform. At shallow depths, high fluid pressure likely influenced the up-dip limit of seismic activity. The high velocity bodies lie above portions of the plate interface where there was reduced coseismic slip and minimal postseismic activity. The northern velocity anomaly may have acted as a structural discontinuity within the forearc, influencing the pronounced crustal seismicity in the Pichilemu region. Our work provides evidence for how the ancient geological structure of the forearc may influence the seismic behaviour of subduction megathrusts.

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Crustal thickness and mantle wedge structure from receiver functions in the Chilean Maule region at 35°S

Cited by 11 publications

References 25 publications

Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

Remarkably consistent thermal state of the south central Chile subduction zone from 36°S to 45°S

Anatomy of a megathrust: The 2010 M8.8 Maule, Chile earthquake rupture zone imaged using seismic tomography

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