Characteristics of gravity field before the Lushan M_S7.0 earthquake based on time variable gravity data from GRACE satellite

Based on monthly gravity data from GRACE satellite, this paper analyzes the characteristics of dynamic changes in gravity field before the Lushan M_S7.0 earthquake by multi-scale wavelet decomposition method. Results show there is a regulation of the dynamic variations in the cumulative gravity field and differential ones. In the time domain, taking the annual average value of gravity field in 2003—2004 as the base value, the annual variation characteristics of gravity field in 2009—2012 are similar to those in 2005—2007. On the basis of the annual average value of gravity field in 2009， the annual changes in gravity field from 2009 to 2012 exhibit a process, i.e., increasing → decelerated increa-sing → accelerated increasing or increasing → slightly descending → rapidly increasing. In the spatial domain, the positive gravity variations are characterized by the process that the epicentral location moves from the center of positive gravity variations to its border, and then to the center of the four-quadrant distribution. So dynamic changes in the gravity field and wave field separation results of the Lushan M_S7.0 earthquake are consistent to the regional deformation characteristics resulted from the Lushan earthquake as a thrust-nappe and strike-slip earthquake.