Study of the structure and seismicity of the February 27, 2010 Chile Mw 8.8 earthquake rupture zone

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The principle aims of the group proposal are described in the summary document. The main objective of the proposed project is to further our understanding of the relationships between great earthquakes, the structure of convergent margins and postseismic relaxation processes using the earthquake sequence along the Southern Chilean margin which started on 27 February 2010 with the Mw 8.8 Maule earthquake. This sequence provides an unprecedented opportunity to image the aftershock activity in great detail and structure of the rupture zone of a great earthquake, and to determine an accurate velocity model for the region. A dense network of 142 seismograph stations was installed by various international teams shortly after the mainshock along the entire 500 km long rupture zone. In the first stage of the project, aftershocks will be detected and located using absolute and relative hypocentre location techniques. The spatial-temporal behaviour of the aftershocks reflects postseismic relaxation processes and the structure therein. The aftershocks will help to clarify how stress is released in the postseismic phase of a great earthquake, and will resolve structures within the shallow part of the subduction zone. Local earthquake tomography will be applied to determine the velocity model. In order to process the large amount of seismogram data of the ongoing aftershock series previous (semi-)automated techniques will be applied, tested and improved. A pronounced and ongoing cluster of crustal seismicity around the city of Pichilemu, including a normal faulting aftershock of magnitude Mw 6.9 will be one of the focus areas. The aim will be to eludicate the reason for these extensional events in the convergent subduction zone setting. A comparison with other subduction zone settings is suggested to better understand the regional seismotectonic situation of the great 2010 Maule earthquake sequence.