Crustal And Upper Mantle 3-D Shear Wave Velocity Structures Beneath Xinjiang Tarim Basin And Its Adjacent Regions

The Tarim Basin and its adjacent regions, which are the focus of the study, have been a prime place to understand the processes of continental collision, the mechanism of mountain building and the interaction of tectonic blocks., including the largest active intracontinental Tianshan orogenic belt, Junggar Basin and Tarim Basin. The data used in this study include 9 months(January to September 2009)of three component continuous seismic data and the teleseismic earthquake data from January 2006 to December 2007 recorded at 74 seismic stations of the newly updated China Provincial Digital Seismic Networks and the regional Kyrgyzstan and Kazakhstan networks.Frist we calculate the receiver functions from the teleseismic P waveform. The results show that the crustal thickness ranges from 35 km to 72 km, the Moho depths of the Tarim Basin and Junggar Basin margin are much thinner than the Tianshan orogen, and the Moho depth beneath the southwestern Tianshan is up to 72 km. The Tianshan orogenic belt crustal thickness shows a thickening trend from the south to the north. The Vp/Vs ratio is in the range of 1.55~1.90, and the Poisson ratio in the Tianshan orogenic belt is relatively high. Then we conduct ambient noise seismic tomography to obtain the Rayleigh wave phase velocity dispersions from 8 s to 40 s and two-plane-wave tomography from 29 s~143 s.Finally, we jointly invert P wave receiver functions with surface wave dispersion to estimate the 3D shear wave velocity structure of the crust and uppermost mantle. The 3D crustal and upper mantle sturcture in the study area shows an obvious horizontal and vertical heterongeneities, which the Tarim Basin underthrusts beneath the southern Tianshan orogen. The low velocity zones in the upper mantle beneath the western Tianshan, may indicate that the continental orogenic process in the Tianshan Mountain is not confined to the crust only, and it is inferred that the deformation of lithosphere delamination man cause the small scale convection in the upper mantle...