High resolution crustal model of SE Tibet from joint inversion of seismic P-wave travel-times and Bouguer gravity anomalies and its implication for the crustal channel flow

Abstract

We present a high-resolution 3-D crustal model of southeastern Tibetan Plateau (SE Tibet) by joint inversion of local earthquake P-wave travel-times and Bouguer gravity anomalies. The joint inversion improves the resolution compared with travel-time-only tomography and more clearly depicts the spatial distribution of low velocity zones in the crust. Our joint inversion model finds no evidence for crustal channel flow in this part of SE Tibet. However, our velocity model shows three distinct low velocity zones in the mid-crust which are generally associated with the major fault systems that control the deformation of SE Tibet in the Cenozoic. The thick, mafic/ultramafic underplating beneath the Emeishan Large Igneous Province effectively blocks the crustal flow from Tibetan Plateau and the crustal low velocity zone beneath the Luzhijiang Fault and Xiaojiang Fault is more likely due to localized asthenospheric upwelling. At the southern end of Nujiang Fault, the joint inversion model reveals the magmatic system beneath the Tengchong volcano that facilitates melt migration from uppermost mantle to the magma chambers in the upper-to-mid crust.