Effects from the Wenchuan Earthquake and seismic hazard in the Longmenshan Mountains at the eastern margin of the Tibetan Plateau

摘要

Effects from the disastrous Ms 8.0 Wenchuan Earthquake of May 12,2008 show that the seismic hazard is closely related to the proximity of active faults and elevated areas of unstable rock as well as the recurrence rate of large earthquakes. Dextral-slip thrusting in the Longmenshan Mountains formed large displacement along -250 km of the Central Longmenshan Fault and smaller offsets along sub-parallel faults. The distribution pattern of the major destruction has a strong northeast-southwest orientation closely related to the ruptured faults and decreases noticeably 3-5 km away from the Central Longmenshan Fault and ~2km from the other faults. Thousands of landslides, rock falls and debris flows triggered by the earthquake lie chiefly adjacent to the principal fault, and smaller-scale landslides along the other faults as well as in distant areas. Some landslides formed dams whose impounded waters threatened downstream cities. Future landslides, rock falls and debris flows will result from rock loosened by the earthquake during rainy seasons or subsequent earthquakes.