Structure of the crust and upper mantle beneath the southeastern Tibetan Plateau by P and S receiver functions

Combined P and S receiver functions from seismograms of teleseismic events recorded at 25 temporary broadband seismic stations in the southeastern Tibetan Plateau are used to map the Moho depth, Poisson's ratio and the thickness of the mantle transition zone. The main results are as follows: (1) The crustal thickness gradually decrease from similar to 60 km in Songpan-Ganze terrane and Qiangtang Terrane to similar to 38 km in Indochina block and similar to 42 km in Yangtze block. (2) The Poisson's ratios in Qiangtang terrane mainly range from 0.25 to 0.28, which indicate that the crust is mainly composed of intermediate and mafic rocks and may be caused by the increased mafic rocks in lower crust. But the Poisson's ratios range from 0.25 to 0.26 in Songpan-Ganze terrane, Indochina block and Yangtze block, which indicate that the crust is predominantly felsic and intermediate rocks. The lack of consistent high Poisson's ratio (>= 0.30) shows that widespread partial melt does not exist within the curst, but does not exclude the presence of local partial melt. (3) There is an obvious thickened zone of the mantle transition zone compared with IASP91 standard value which varies from 10 km to 26 km in Qiangtang terrane. The anomaly suggests that the temperature is about 100 degrees C to 260 degrees C lower than global average value within the mantle transition zone, and it may be attributed to the presence of a subducted slab within the mantle transition zone.