Seismic Potential along the Main Active Strike-slip Fault Zone in Western Sichuan, China

摘要

The 900-km-long main strike-slip fault zone of western Sichuan has been exhibiting strongly left-lateral faulting. This is one of the major seismogenic belts in southwestern China. This paper combines geologic and liistoric-earthquake information to evaluate quantitatively seismic potential along this fault zone. Average slip-rates along the fault zone have been recalculated or rccstimaled. Based on fault geometry and space-time pattern of historical earthquake raptures, this fault zone has been divided into 16 segments. Combining estimated co-seismic slips, historic and prehistoric event timings, as well as using the time-predictable and renewal models, the author estimates the average recurrence time between earthquakes for each fault segment. Further, the probabilities of future segment-rupture earthquakes have been computed by employing the evaluating model of time-dependent probabilistic seismic hazard, The main results show as Follows: (1) Till A.D. 2026, 6 out of the 16 segments have relatively high cumulative probabilities (>0.45). These 6 segments are all located at the seismic gaps that have been not ruptured for at least 100 years.(2) In the coming 30 years (1996-2026), not all these 6 segments have relatively high conditional probabilities, because most of them have longer average recurrence times or shorter elapsed times relative to the average recurrence times. (3) On the basis of comparisons among the probabilities of Die individual segments, it is suggested that two areas, from Mianning to Kangding (segments 8 to 11) and from Shimian to Xichang (segments 14 to 15), should be considered as relatively risk area along the fault zone in the coming years.