Crustal structure beneath northeastern Tibetan Plateau from teleseismic receiver functions and its relationship with the regional seismicity

English Abstract:

More detailed studies of crustal structure in northeastern Tibetan Plateau can be of great benefit to the understanding of crustal deformation and plateau growth mechanisms. We investigate crustal structure beneath 58 seismic stations in northeastern Tibetan Plateau by using the P receiver function method to estimate the crustal thickness, Poisson’s ratio and Vp/Vs ratio by analyzing the collected three-component teleseismic data. These data are recorded by 29 stations deployed by China University of Geosciences between June 2008 and July 2010, 19 Ascent stations deployed between May 2007 and August 2008, 2 stations from China National Seismic Network and 8 stations from Central China Network. The images of Moho depth suggests the lateral variations of the crustal thickness decreasing from Qilian Orogen (~63 km) to east Kunlun fault area (~40 km). High Vp/Vs and Poisson’s ratio appear along a narrow band from southwest to northeast in the east Kunlun fault area, while lower Vp/Vs and Poisson’s ratio appear in the Qilian Orogen.The observations disagree with the crustal composition beneath the northeastern margin of the Tibetan plateau. There is no simple correlation between the regional seismicity and the crustal thickness observed here. Our results of crustal structure and seismicity in this study area not only reveal the lateral inhomogeneity of the crustal structure but also provide some constraints on understanding the mechanism of uplift and crustal thickening of the Tibet.