Searching for Buried Fault under Chengdu Plain Using Gravity Anomaly Survey

The 2008 Wenchuan Ms 8.0 earthquake resulted in big number of casualty and heavy strike to the local economy. Chengdu Plain has received highly priority on earthquake risk evaluation due to its dense population and short distance to the highly active Longmenshan fault zone. We conducted mapping of gravity anomaly of Chengdu Plain in order to locate the possible buried fault zones between the northwest Longmenshan and southeast Longquanshan. In this investigation, 192 relative gravity data have been collected along six profiles with each extending about 70 km across the plain area. The Bouguer gravity anomaly has been calculated for generating the large-scale anomaly trend on the surface. Preliminary data analyses showed rough indications of a major fault zone along Xinjin-Chengdu-Deyang and a relative small fault zone near Zhuwapu, Dujiangyan, northwest Chengdu Plain. The detail of the buried geological structures will be further investigated based on the upward continuation of the surface anomaly data and residual gravity anomaly of the surveying area.