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.
