The Crust and Uppermost Mantle Structure in Northeastern Tibet by Joint Inversion of Receiver Functions and Surface Wave Dispersion

Tuesday, 16 December 2014
Yangfan Deng1,2, Weisen Shen3, Tao Xu2, Zhenbo Wu2, Xinlei Sun1 and Michael H Ritzwoller3, (1)GIG Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Isotope Geochemistry, Guangzhou, China, (2)IGG Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, (3)University of Colorado at Boulder, Physics, Boulder, CO, United States
As the NE margin of the Tibetan plateau, Northeast Tibet doesn’t have the steep topography as east Tibet and west Tibet, and as an important tectonic junction, it is an ideal site to study the formation and uplift of the plateau. Recent seismic investigations have paid attention to this region, while we still can’t figure out the Moho depth as they give different results. To better understand the crustal structure in Northeast Tibet, our passive seismic experiment was carried out from Songpan-Ganzi block to Qilian block. After a series of data process on the receive function, we get a fine structure along this profile by joint inversion of receive function and surface wave with Bayesian Monte Carlo inversion. The final results show that the Moho depth uplifts from 65 km to 55 km from south to north, and there are double Moho reflections in the north. The crustal structure is various in Songpan-Ganzi block, Kunlun block and Qilian block, as the low velocity in middle and lower crust is remarkable beneath Songpan-Ganzi block, while there are no low velocity beneath Qilian block, which present the difference between plateau and surrounding regions, and indicate the lateral spreading of the Tibetan Plateau.