Gravity Variation Observed by Scientific Expedition of Lushan Earthquake
1〓College of Earth Sciences, University of Chinese Academy of Science, A 19 Yuquan Road, Beijing 100049, China
2〓Key Laboratory of Earthquake Geodesy, Institute of Seismology,CEA,40 Hongshance Road, Wuhan 430071, China
3〓Wuhan Base of Institute of Crustal Dynamic,CEA,40 Hongshance Road, Wuhan 430071, China
4〓Surveying Engineering Institute, Earthquake Administration of Sichuan Province,139 Shangba Road, Ya’an 625000, China
5〓First Crust Monitoring and Application Center,CEA,7 Naihuo Road, Tianjin 300180, China
6〓Second Crust Monitoring and Application Center, CEA, 316 Xiying Road, X i’an 710054, China
Abstract:By using gravity data in the area of the scientific expedition of the Lushan earthquake, we have systematically obtained the gravity variation before and after earthquake. The results show that:1) before the earthquake, the area beside the Longmenshan fault shows an obvious anomaly, and some high gradient zones are parallel or vertical with the Longmenshan, Xianshuihe and Daliangshan faults| 2) after the earthquake, gravity variation was opposite in the area beside the Longmenshan fault| 3) heat and bulge of the material of middle and bottom crust probably cause the gravity variation and may be one important trigger factor of the Lushan earthquake.