Asperity of the 2013 Lushan earthquake in the eastern margin of tibetan plateau from seismic tomography and aftershock relocation

Abstract

The Mw 6.6 Lushan earthquake occurred on 2013 April 20 in the eastern margin of Tibetan Plateau, and was about 50 km away from the 2008 Mw 7.9 Wenchuan earthquake rupture zone. By using arrival times from portable and permanent seismic stations, local earthquake tomography and aftershock relocation were conducted by using 41 955 rst P and 42 687 rst S arrivals. Low-Vp/Vs, high-Vp and Vs anomaly are found in the source region, which is well consistent with the aftershock distributions. The ruptured fault plane might be a blind thrust and is well dened by the Vp/Vs structure and aftershock seismicity. High-velocity and low-Vp/Vs anomalies may suggest the mac or ultramac materials thrust from mid-lower crust, and dene the asperity that concentrated stresses responsible for seismogenesis. In contrast, low-Vs anomaly is found in the gap between theWenchuan and Lushan earthquakes, suggesting of ductile rocks with low stress. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.