Deep ruptures around the hypocenter of the 12 May 2008 Wenchuan earthquake deduced from aftershock observations

摘要: Abstract On 12 May 2008, a great earthquake of Mw 7.9 occurred in Wenchuan, China. To record its aftershocks and investigate the distribution deep ruptures associated with event, we deployed temporary short-period seismic network around epicenter soon after had occurred. A total 6036 were located from 108 days data high signal-to-noise ratio, collected July to October 2008. These further processed using double-differential location method, 2878 retained relocated clusters. According aftershocks, refined main shock hypocenter 31.001°N, 103.280°E, 17 km deep. The spatial reveals interesting features ruptures: (1) most are upper crust at depths shallower than 20 km, beneath surface outcrop Pengguan massif, indicating that is brittle seismogenic brittle–ductile transition between middle crust; (2) NW–SE-striking low-seismicity zone crossing through Yingxiu Town divides study area into two blocks contrasting distributions seismicity, suggesting different rupture characteristics either side line; (3) upward extrapolation aftershock clusters intersects southern northern arms Zipingpu Reservoir, future seismicity along reservoir activated by Wenchuan will be influenced impoundment/drainage for several decades come.