Block model and dynamic implication from the earthquake activities and crustal motion in the southeastern margin of Tibetan Plateau

After analysis of the current crustal deformation field from GPS data, the slip characters of active faults, the surface ruptures of historical earthquakes, and the focal mechanisms of the recent earthquakes, the southeastern margin of the Tibetan plateau was divided into 11 sub-blocks, including the West Qinling sub-block, Aba sub-block, Longmenshan sub-block, Zangdong sub-block, Yajiang sub-block, Shangri La sub-block, Dianzhong sub-block, Baoshan sub-block, Jinggu sub-block, Mengla sub-block and the Ximeng sub-block. The present-day translation and rotation rate of the sub-blocks, also the slip rate of the boundary faults, were calculated using the GPS data. The results show the following characters: Each sub-block has its movement changed after the specific main stress action from the adjacent sub-blocks. Among these sub-blocks, the rotations of the Baoshan sub-block, Zangdong sub-block, Yajiang sub-block, Shangri La sub-block, Dianzhong sub-block, are more obvious than others. Corresponding to the rotations above, the boundary faults among these sub-blocks behave differently. Among these fault activities, the compressions between the Zangdong and Yajiang sub-blocks, as well as between the Yajiang and Dianzhong sub-blocks are obvious. Based on the results above, we discussed the current crustal motion characters of the southeastern margin of the Tibetan plateau. The lateral extrusion of the rigid blocks and gravity collapse of the crust co-exist in the region, which are induced mainly by the "channel flow" of the lower crust, and partly enhanced by the tensile force from the Burma plate due to its counter-clockwise rotation.