Moscoso, Eduardo, Grevemeyer, Ingo , Contreras-Reyes, Eduardo , Flueh, Ernst R., Dzierma, Yvonne, Rabbel, Wolfgang and Thorwart, Martin (2011) Revealing the deep structure and rupture plane of the 2010 Maule, Chile earthquake (Mw=8.8) using wide angle seismic data. Earth and Planetary Science Letters, 307 . pp. 147-155. DOI 10.1016/j.epsl.2011.04.025.

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Abstract

The 27 February, 2010 Maule earthquake (Mw=8.8) ruptured ~400 km of the Nazca-South America plate
boundary and caused hundreds of fatalities and billions of dollars in material losses. Here we present
constraints on the fore-arc structure and subduction zone of the rupture area derived from seismic refraction
and wide-angle data. The results show a wedge shaped body ~40 km wide with typical sedimentary velocities
interpreted as a frontal accretionary prism (FAP). Landward of the imaged FAP, the velocity model shows an
abrupt velocity-contrast, suggesting a lithological change which is interpreted as the contact between the FAP
and the paleo accretionary prism (backstop). The backstop location is coincident with the seaward limit of the
aftershocks, defining the updip limit of the co-seismic rupture and seismogenic zone. Furthermore, the
seaward limit of the aftershocks coincides with the location of the shelf break in the entire earthquake rupture
area (33°S–38.5°S), which is interpreted as the location of the backstop along the margin. Published seismic
profiles at the northern and southern limit of the rupture area also show the presence of a strong horizontal
velocity gradient seismic backstop at a distance of ~30 km from the deformation front. The seismic wide-angle
reflections from the top of the subducting oceanic crust constrain the location of the plate boundary offshore,
dipping at ~10°. The projection of the epicenter of the Maule earthquake onto our derived interplate boundary
yielded a hypocenter around 20 km depth, this implies that this earthquake nucleated somewhere in the
middle of the seismogenic zone, neither at its updip nor at its downdip limit.

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