Crustal and upper mantle velocity structure in the northeastern Tibetan Plateau

The Indian-Eurasia continental collision has led to the uplift of the Tibetan Plateau, and various competing models have been proposed to explain the rise and growth of the Tibetan plateau. The best place to address the growth of the Tibet plateau and to test the competing models is the northeast Tibetan plateau. What causes the rise of the northeast Tibetan plateau? Is it the mid-crustal flow, the coherent thickening of the Tibet lithosphere, or the subduction of the Eurasian blocks? Therefore, we combined both ambient noise data and earthquake Rayleigh wave data to estimate both the group velocity structure and the S-wave velocity structure across the northeastern margin of the Tibetan Plateau (E88 -108 , N32 - 42 ). Our preliminary results show that in the crust, the low-velocity anomaly beneath the Tibetan Plateau has not been observed beneath the Qaidam basin, south Kunlun block and Qinling Orogen, suggested that the eastern KunLun fault interrupted the crustal low-velocity flow. However, our results display that the low-velocity zone appears beneath the Qilian Orogeon, suggestive of complex tectonic processes in the northeastern margin of the Tibetan Plateau. In the upper mantle, from 150 km to 250 km, our shear wave velocity model shows a low velocity channel beneath the Qaidam-Qilian-Qinling block which may represent the asthenosphere. We also did some inversion tests for the anisotropy parameters. Our preliminary results show that the dominant fast direction is NWW-SEE, generally consistent with the SKS splitting results.