Velocity field for crustal deformation in China derived from seismic moment tensor summation of earthquakes

摘要

The intraplate motion is studied in the territory of China where about 150 polygonal seismic sources are considered and grouped on the basis of the available fault plane solutions, large known faults and level of seismic activity. Every polygon is divided into several triangles and velocities at the triangle vertices are determined from the available moment rate tensors by assuming a linear continuity of the velocity field within each triangle. The estimation of the moment rate tensor is partitioned in the unit-scaled moment tensor obtained by the available fault plane solutions of large event (Mgreater than or equal to5.0) after 1900, which define the type of deformation and the scalar annual moment rate, obtained by the complete seismicity catalogue which defines the rate of seismic deformation. The results show that the convergence between India and Eurasia is about 50 nim/year with Eurasia fixed, while the eastern part of China moves eastwards at about 8 - 10 mm/year. The motion direction changes gradually from northeastward around the Himalayan region to southeastward around the Red River fault and to southwestward around eastern Himalayan Syntaxis, which partially compensates the penetration of the Indian plate. A sharp change of the velocity gradient was found near the southeastern part of Tibet plateau, the Qilianshan region and Fuyun fault where large strain rates are released due to strong earthquakes there. The results are supported by recent horizontal GPS motion model and other independent evidence. The motion pattern between the Altun-Qilianshan-Longmenshan faults and the Himalayan fault in Qinghai-Tibet region strongly suggests that this area exhibits a more or less continuous deformation pattern rather than a rigid block behavior. (C) 2002 Published by Elsevier Science B.V. [References: 62]