Crustal structure in the Yunnan region determined by modeling receiver functions
用接收函数方法研究云南及其邻区地壳上地幔结构

We selected broadband teleseismic waveform data recorded by the Yunnan Seismic Network and CDSN to study the crustal structure in Yunnan and its adjacent region. The crustal thickness and Vp/Vs ratio are estimated by the grid-search method using crustal conversion and multiples, assuming an average P-wave velocity in the crust. Teleseismic P waveform modeling is carried out to investigate the S-wave velocity structure, assuming the fixed Vp/Vsvalue inferred from the grid-search method. The results from the two estimation techniques were consistent. Our results show strong lateral variations in crustal thickness in this area. Our results also indicate that there exist low velocity zones and high Vp/Vs beneath the Yunnan region, especially in western Yunnan. All these are the possible evidence of the crustal flow in middle-to-lower crust, which are responsible for the thickening of crust. The Vp/Vs and crustal thickness are different across the Red-river fault, which implies that the Red-river fault is one main boundary fault. Combining results from other geophysical investigations, we conclude that both the Simao terrane and Baoshan-Tengchong terrane belong to the Gondwana plate.