Crustal thickness in southeast Tibet based on the SWChinaCVM-1.0 model

Abstract

Extensive geophysical research has been carried out in southeast Tibet due to the complex geological structure and high seismicity. The study of the Moho interface can provide useful information for the geophysical research. SWChinaCVM-1.0 is the first version of a regional community velocity model for the Sichuan-Yunnan region and aims to provide a reference for seismological research in the region. Based on this model, a high-precision community Moho interface model can be obtained using common conversion point (CCP) stacking, to further expand the applicability of SWChinaCVM-1.0. Before CCP stacking, it is necessary to check the fit of the practical and theoretical travel times of the Ps phase and its multiples under the constraints of the model. Using this method, referred to as H-κ0 stacking, we determined the Moho interface. However, the multiples were poorly fitted with the theoretical travel times at many stations, and the crustal thickness obtained was inconsistent with previous findings. Therefore, we speculate that the SWChinaCVM-1.0 model has some limitations that render it incompatible with the CCP stacking method. To further verify this hypothesis, we performed H-κ stacking using the vP-vS model, vP model, vS model, and the regional average velocity vP0 and compared the results with those of H-κ0 stacking. The results of the comparison indicate that the SWChinaCVM-1.0 model requires improvements. In addition, by analyzing the SWChinaCVM-1.0 inversion process, we found that the vS model was more reliable than the vP model. Finally, we adopted the crustal thickness obtained using H-κ stacking based on the vS model as the initial version of a community Moho interface model for the Sichuan-Yunnan region (SWChinaCVM-MOHO-1.0).