Numerical Simulation of Annual Change Patterns of Contemporary Tectonic Stress-Strain Field of the Chinese Mainland

摘要

Based on the active crustal block structures, the Holocene active faults and the wave velocity structures with a resolution of 1°×1°, a two-dimensional finite element model for the tectonic stress-strain field of the Chinese mainland is constructed in the paper. Using GPS measurements, the velocity boundary conditions for the model are deduced, then, the annual change patterns of the present-day stress-strain field of the Chinese mainland are simulated. The results show that (1) the general pattern of the recent tectonic deformation in the Chinese mainland is governed by the interactions of its surrounding plates, of which, the Indian Plate plays a major role. There is a NNE-directed velocity distribution in the west of the Chinese mainland. The maximum slip rate appears at the collision boundary. The north-directed components decrease, while the east-directed components increase gradually from south to north and from west to east. In the east part, there is a general east-directed movement, with a certain amount of south-directed components. (2) The present-day tectonic stress field in the Chinese mainland has undergone the process of enhancement in recent years, and this process presents a general pattern of radiating eastwards from the Qinghai-Xizang (Tibet) Plateau as the center. The general pattern is similar to the ambient tectonic stress field, indicating the inheritance of contemporary tectonic deformation on the Chinese mainland. (3) The maximum principal strain presents an obvious pattern of being high in the west and low in the east. The tectonic movement in the west is stronger than that in the east. Large active faults are all located in the high-value zones of maximum principal strain. However, the magnitude of strain is smaller in the interior of the active crustal blocks, which are enclosed by these faults. (4) The stress-strain field of the Sichuan-Yunnan region is unique. It may not be governed by collision of plates alone but a combination of the movement of peripheral active blocks, material flow in the lower crust or upper mantle and special tectonic geometry (such as the eastern Himalayan syntax) as well.