关键词: 川滇地区, 活动块体边界断裂, 滑动速率, 应力累积速率分布

Abstract: Based on current cognition of the division of active block and fault system in the Sichuan–Yunnan region, we build a two–dimensional finite–element contact model, including the primary block boundary faults. Slip rate and stress accumulation rate distribution of the primary block boundary faults are obtained by using long–term GPS observation data from 1991 to 2015 and "block–loading" method. Combined with focal mechanisms and seismic activity, we discuss the relationship between slip rate distribution, transfer and stress transformation in large left strike-slip fault zones, tectonic mechanism with normal fault type and the probable cause of the seismic discrepancy between the north and south segments of the Red River fault. The main conclusions are as follows: (1) East Kunlun and Xianshuihe–Xiaojiang fault zones, when the north-west-striking turn to nearly north-south-oriented, partially strike slip is absorbed by the fault-bend parts and then converts into stress accumulation. (2) Affected by the left–lateral shear of Xiaojiang fault, south-central segment of Red River fault is dominated by right–lateral slip with weak extrusion. North segment of Red River fault is dragged by the south-central and right-lateral slip, together with the Jinsha River fault and Deqin–Zhongdian fault, constitute a right-lateral shear deformation zone with right–order oblique type. The normal focal mechanisms are predominantly distributed within this zone. (3) The north segment of Red River fault appears to be slightly tensional. However, the south segment appears to be weak extrusion. Therefore the north section is easier to rupture and seismic activity is significantly stronger than the south-central section.

Key words: Sichuan–Yunnan region, Active block boundary faults, Slip rate , Stress accumulation rate distribution