Crustal structure beneath the eastern margin of the Tibetan Plateau and adjacent areas from receiver function stacking and gravity modeling

To provide constraints on the mechanisms responsible for the uplift and crustal thickening of the eastern Tibetan Plateau, the thickness and Vp/Vs values of the Moho beneath 153 seismic stations are obtained by stacking P-to-S converted phases from the Moho and gravity modeling. The resulting crustal thickness generally decreases from the northwest to the south-east, from about 60 km in the Bayan Har Block to 30 km in the Sichuan Basin. The crustal Vp/Vs measurements in the Qinling Orogenic Belt, Bayan Har Block, Chuxiong Basin, and Yangtze Platform indicate an overall intermediate to felsic crustal composition. With a relatively thick crust, the inferred crustal Vp/Vs beneath the Bayan Har Block indicates that crustal shortening is accomplished by brittle crustal thickening between rigid crustal blocks, a conclusion that is in line with the observed density structure derived from Bouguer gravity data. High crustal Vp/Vs values up to 1.96 are observed along the Xianshuihe and southern Longmenshan faults. The observed spatial distribution of crustal properties is in agreement with the hypothesis that strain partitioning across deep-rooted faults and the presence of a localized crustal channel flow system both play a vital role in the lateral expansion of the eastern Tibetan Plateau --Abstract, page iii