A study on deep structure using teleseismic receiver function in Western Yunnan

1 Tectonic environment and geophysical background There are two kinds of continental-oceanic contacts relationship: the Atlantic and the Pacific type. The Atlantic type is characterized by extension and lower relative activity. The continent nearby the ocean is stable and its edge is of extension and block tectonics. Europe, Africa and American belong to this kind. The Pacific type is characterized by compression and shear com-pression. The continent near the ocean is more active than othe…

A study on deep structure using teleseismic receiver function in Western Yunnan

s Western Yunnan is located at the boundary of collision or underthrusting zone of Eurasian plate and is influenced by many times tectonic movements. With very complex geological environment and tectonic background, it is one of the seismically active areas. In the paper, the teleseismic records were selected from 16 national, local and mo-bile stations, including 4 very-wide-band mobile stations of PASSCAL. And nearly 2 000 receiver functions were extracted. Two measuring lines are 650 km and 450 km, respectively and across some major tectonic units in Western Yunnan. It is indicated that Nujiang might be a seam characterized by underthrusting. The western and eastern boundaries of Sichuan-Yunnan rhombus block, i.e., Honghe and Xiaojiang faults, might be an erection seam or collision belt. Panxi tectonic zone still has the characteristics of continental rift valley, that is, the surface is hollow and the upper mantle is upwarping. The tectonic situation in Western Yunnan is of certain regulation with the interlacing distribution of orogenic zone and seam. The crustal thickness decreases gradually from the north to the south and the S wave velocity is globally lower here.