Block division and motion of the Tibetan Plateau and surrounding regions

The collision of the Indian plate and the Eurasian plate caused the uplift of the Tibetan Plateau, which is characterized by widespread active faults and associated seismic activity. The surface velocities derived by Global Position system (GPS)  indicate that the plateau is moving northeast and southeast relative to the stable Eurasian. An accurate description of the deformation field of this plate boundary zone is crucial for understanding the long-term crustal deformation and tectonic processes of the continent, and has important significance for lithospheric dynamics and seismic risk assessment. Based on the tomography, active fault distribution and previous studies, we constructed a block model with 15 primary blocks and 15 secondary blocks to describe the block motion of the Tibetan Plateau and surrounding regions. In the block model approach, the lithosphere is divided into many blocks, each of which follows the kinematic rules of plate tectonics, the velocity at any point in the block can be described in terms of rotation around the Euler pole, and the strain occurs only at the boundaries of blocks. We used 3193 GPS data to simultaneously invert the  fault slip rates of the boundaries of blocks and the Euler pole and angular velocity of the block rotation. The inversion results show that large fault slip mainly occurs on the block boundaries of southern and southeastern Tibet, and the slip rate of the major faults is roughly the same as that of the geological results. The rotation velocities of the blocks in the south and southeast of the Tibetan Plateau is about 1 deg/Myr, and the rotation direction is counterclockwise. The rotational angular velocity of the eastern and northern blocks in the study area is about 0.1 deg/Myr, and the fault slip rate of the block boundaries is mostly less than 5 mm/yr, which is relatively stable. We found that there are large residuals in the south and southeast of the Tibetan Plateau. The tectonic background in this area is complex, and its deformation may be greatly affected by other factors. The precise definition of block geometry needs to be further improved.

Research members: Feifan Ye, Dr. Yan Hu