Characteristics of satellite-gravity variations in the North-South Seismic Belt before the 2013 Lushan earthquake

To study the characteristics of gravity variations in and near the North-South Seismic Belt before the 2013 Lushan earthquake,we used the geopotential-field models based on monthly data of the RL05 GRACE satellite to calculate the gravity changes.Here we present the patterns of annually cumulative variation,differentiatial variation and secular trend,as well as the continuous time-series at 4 characteristic sites during 2004-2012.The result shows that the anomalous positive-to-negative transition zone,in which the epicenter of the 2008 Wenchuan earthquake was located,did not show any new gravity change before the Lushan earthquake,though located in the same zone.