Dense profile probing depth extent of Pengguan Complex and Longmenshan Fault

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The main aim of this project is to investigate the deep structure beneath the Longmenshan fault zone in China, based on a very dense passive seismological profile. The Longmenshan fault zone hosted the Wenchuan earthquake of May 2008 with a magnitude (Mw) of 7.9 and the Lushan earthquake of June 2013 with a magnitude (Mw)of 6.6. Since 2008, several deep boreholes have been drilled along the fault zone about 40 km northeast of the epicentre of the Wenchuan earthquake. It is planned to mainly use the receiver-function method, to investigate the deep structure and, in particular, the structure of the Moho. Other recent experiments at the borders of Tibet have shown that the region of the lower crust, including the Moho, play an important role in the growth of the plateau.It is planned to deploy about 40-50 broadband seismic stations along the profile in spring 2018. The stations should be serviced every six months and it is planned to demobilize the stations in the autumn of 2019. The station spacing will be about 10 km at both ends of the profile. In contrast, the station density will be increased in the middle of the profile, so that the station spacing in the vicinity of the Longmenshan fault zone will be just 1-2 km. With this higher station density in the vicinity of the Longmenshan fault zone, the aim is to open the possibility of imaging structures in the crust such as the base of the Pengguan complex or the Longmenshan fault zone itself. Due to the boreholes in the region it is known that the Longmenshan fault zone is a fairly steeply dipping structure in the upper crust. Nevertheless, the group at GFZ Potsdam has succeeded in imaging with the receiver-functions method, a steeply dipping structure in the Pamir, namely the Pamir seismic zone. If we can image such structures, then we can perhaps contribute to understanding the hazards posed by the earthquake threat in the region.