Characteristics of subsurface density variations before the 4.20 Lushan M_s7.0 earthquake in the Longmenshan area: inversion results  

作　　者：Songbai Xuan Chongyang Shen Hui Li Hongtao Hao 

机构地区：[1]School of Geodesy and Geomatics,Wuhan University [2]Institute of Seismology,China Earthquake Administration

出　　处：《Earthquake Science》2015年第1期49-57,共9页地震学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (41304060);the National Key Basic Research Program of China (973 Program, 2013CB733305);Scientific Investigation of April 20, 2013 M7.0 Lushan, Sichuan Earthquake

摘　　要：The 4.20 Lushan Ms7.0 earthquake occurred on the southwest segment of the Longmenshan fault on 20 April 2013. Some meaningful information on the prepa- ration and occurrence of this earthquake was found based on the dynamic variation of gravity （DVG）. To examine the great progress of the Lushan earthquake, we obtained the density variation （DENV） derived from the DVG using the compact gravity inversion method in this article. The inversion results reveal three main findings： （1） the DENV in the crust in the Jinshajiang fault area changed from positive in 2010-2011 to negative in 2011-2012. （2） The DENV in the Xianshuihe fault area decreased continuously from 2010 to 2012. （3） The DENV of the uppermost mantle of South China decreased in 2010-2011 and increased in 2011-2012. We propose that the flow/expansion of the middle-lower crust beneath the Bayan Har block and Moho subsidence on the southwest margin of the Chuan-Dian block may have been the major causes of the Lushan earthquake.The 4.20 Lushan Ms7.0 earthquake occurred on the southwest segment of the Longmenshan fault on 20 April 2013. Some meaningful information on the prepa- ration and occurrence of this earthquake was found based on the dynamic variation of gravity （DVG）. To examine the great progress of the Lushan earthquake, we obtained the density variation （DENV） derived from the DVG using the compact gravity inversion method in this article. The inversion results reveal three main findings： （1） the DENV in the crust in the Jinshajiang fault area changed from positive in 2010-2011 to negative in 2011-2012. （2） The DENV in the Xianshuihe fault area decreased continuously from 2010 to 2012. （3） The DENV of the uppermost mantle of South China decreased in 2010-2011 and increased in 2011-2012. We propose that the flow/expansion of the middle-lower crust beneath the Bayan Har block and Moho subsidence on the southwest margin of the Chuan-Dian block may have been the major causes of the Lushan earthquake.

关 键 词：Density variations Gravity inversion Deepprogress Lushan earthquake 

分 类 号：P315[天文地球—地震学]