CSES Community Velocity Models in Southwest China

Abstract

Southwest China, located at the southeastern margin of the Tibetan Plateau, plays an important role for the plateau growth and its material extrusion. It has complicated tectonic environment and severe earthquake hazards. There have been numerous geophysical studies in Southwest China. However, a community velocity model (CVM) in this region is still not available, which makes it difficult to have a consistent catalogue of earthquake locations and focal mechanisms, and a consistent velocity model for simulating strong ground motions and evaluating earthquake hazards. In this study, we first propose an overall strategy of building multi-scale CVMs in Southwest China. Then we build a high-resolution community velocity model (both Vp and Vs) of the crust and uppermost mantle in Southwest China along with earthquake locations by joint inversion of massive body-wave and surface-wave traveltime datasets. A multigrid strategy is adopted in the joint inversion. The spatial resolution of both Vp and Vs models can reach up to 0.5º horizontally and 10 km vertically according to checkerboard tests. The comparison of our inverted Vp and Vs models with those from other studies show general consistency in large-scale features of velocity anomalies. The inverted models are further validated using various seismic datasets. In general, our velocity models show two low Vp and Vs anomaly zones in the middle-lower crust and a prominent high velocity anomaly region in central Yunnan in between them. Our new models have been serve as the first CVMs in Southwest China (i.e., SWChinaCVM-1.0) for future seismological studies. In addition to the construction of the regional scale CVM in southwest China, other studies have obtained high-resolution velocity models of urban, fault zone, and fault scales using dense array seismic data in some regions in Southwest China. Finally, we discuss some perspective studies related to the construction of multi-scale CVMs in Southwest China as well as community models of other physical parameters.KeywordsSouthwest ChinaCrust and Upper MantleCommunity Velocity ModelJoint Inversion