Abstract:

Based on analysis of strong motion records of Wenchuan Ms 80 earthquake on May 12, 2008, we compared and discussed the distribution characteristics of peak ground acceleration (PGA) and coseismic displacements to disclose the correlation between earthquake intensity distribution and surface rupture. From the recording waveforms of typical nearfault strong motion stations, we can extract valuable information of fault rupture process and behaviors contained in acceleration timehistories, which further confirmed the multirupture process by means of strong motion observation. The results show that the Wenchuan earthquake contained at least 4 times of rupture events during the whole process. The most important first two events corresponded respectively to ruptures occurred in the YingxiuBeichuan fault and the BeichuanNanba fault. The other two events, in which the energy released was relatively small, were triggered probably by the second rupture event occurred on the BeichuanNanba fault. In addition, the peak acceleration perpendicular to the fault indicated that the causative fault was a highangle reverse fault, which is consistent with the results of geological survey and aftershock relocation.

Key words: strong motion records, causative fault, rupture process, highangle reverse fault, Wenchuan Ms 80 earthquake