SEISMIC STUDIES ON THE CRUST-MANTLE STRUCTURE ACROSS KARAMAY-KUCHA IN XINJIANG, CHINA

Reversions as receiver functions and ACH were performed using the teleseismic data acquired from the seismic array that were deployed across Tian Shan in Xinjiang in 1997\|1998 jointly by Sino\|French seismic crew.The results suggest the crustal shortening and thickening in the study area that are well expressed by the thickening in lower crust and the uplifting of Tian Shan in the collision between Euro\|Asian and Indian plates. Underthrusting in the intra\|continental collision model turns out to be asymmetrical, with the northward in the south much stronger than the southward in the north. The cause of the steepness of the southward underthrust is likely to rest on the strong extrusion. Going further deep, the curving end of the cold underthrusting zone may detach, penetrating its own way. The ongoing uplifting of Tian Shan is given birth mostly by the underthrusting on its south and the squeezing force from both sides. The underthrusting zone is composed of compact ancestral crystalline rocks. The thickness of the crust varys from 65km beneath the main body of Tian Shan to 41km beneath the Tarim and Zengar basins on sides with certain degree of thickening. The major faulting zones in the area go precipitously in the scope of crust, with those in the low\|velocity bodies closely associated to the activities of molten mantle materials and seismicity.