Abstract:By processing the remote seismic wave profile data recorded by 36 stations in three parallel rivers region in northwest Yunnan, we extract the radial P-wave receiving function, and obtain the initial models of different regions based on the crustal shear wave velocity model of China Earthquake Science Experimental Field. We adopt the time-domain linear inversion method and bootstrap resampling technique. At last, the S-wave velocity structure under each station is inverted. The results show that: 1) The S-wave velocity structure of the crust in the study region is divided by the Lancang river fault and 27.5°N, showing obvious regional differences. In the upper crust, there is a low-velocity layer extending from the surface to the interior of the crust in the range of 0-25 km in the S-wave velocity, but the thickness of the low-velocity layer varies greatly in different regions. The low-velocity layer is relatively developed north of 27.5°N with a thickness of 20-25 km, and south of 27.5°N with a significant difference in the thickness of the low-velocity layer on the east and west sides of the Lancang River fault. The fault is between 10 km and 25 km to the west and about 4 km to the east. 2) In the lower crust, the S-wave velocity shows the transverse distribution characteristics of “the NE and SW regions are dominated by relatively low velocity, while the NW and SE regions are dominated by relatively high velocity,” which is bounded by the Lancang River fault and 27.5°N. There are low-velocity bodies in the mid-south of the Nujiang fault and the northern part of the Jinshajiang-Honghe fault at a depth of 25-45 km, which are connected with the low-velocity layer of the upper crust. 3) The Lancang river fault is an important interface between crustal thickness and S-wave velocity, and plays a controlling role in the tectonic evolution of three parallel rivers region in northwest Yunnan.
YANG Jianwen,JIN Mingpei,YE Beng et al. Crustal S-Wave Velocity Structure in Three Parallel Rivers Region in Northwest Yunnan[J]. jgg, 2023, 43(10): 1068-1073.