Abstract:In order to acquire the disaster loss assessment data accurately and quickly when a strong earthquake occurs,we need both the detailed information about the structural features of the earthquake occurring region and reliable seismic observation data.After the huge earthquake of Wenchan MS8.0 on May 12th,2008,many observation stations have been deployed and some important research results have been obtained in the Longmenshan fault zone by the China Earthquake Administration （CEA）,which also provided valuable data for investigating the Lushan MS7.0 earthquake of April 20th,2013.By analyzing the seismic waveform data recorded by 70 strong-motion seismographs,we reveal the variation characteristics of the peak ground acceleration （PGA） for different epicentral distances,discuss the spatial acceleration dynamic change and the related waveform propagation features,and calculate the seismic intensity distribution of the Lushan MS7.0 earthquake based on the obtained PGA in this study and empirical formulae.Our results indicate that the highest seismic intensity is about Ⅸ degree and both the Lushan and Baoxing regions are among the severely afflicted areas.Areas in which the seismic intensities are above Ⅷ are mainly located in the center of Lushan and jointly in the regions of Baoxing,Tianquan,Ya＇an,Minshan,etc.Furthermore,seismic intensities above Ⅴ have a NE long axis distribution along both sides of the Guanxian-Anxian fault in the Longmenshan fault zone.The characteristics of the seismic intensity shown in this study are consistent with the results reported by the CEA.In addition,the PGA shows that the initial rupture of the Lushan earthquake has a thrust fault,which agrees well with the focal mechanism solution of Harvard University.It is also noted that the large fault probably has an effect on the PGA distribution.As a result,our method of analysis is feasible and stable,and it can offer important references for earthquake relief work to the government.
