利用GPS和水准测量资料反演2001年昆仑山口西8.1级地震的同震滑动分布

CO-SEISMIC SLIP DISTRIBUTION OF THE 2001 WEST OF KUNLUN MOUNTAIN PASS EARTHQUAKE INVERTED BY GPS AND LEVELING DATA

通过分析 2 0 0 1年昆仑山口西MS8.1地震前后的GPS资料和 1 979— 2 0 0 2年的水准测量资料 ,获得了地表同震位移场。利用这些同震位移数据 ,以震后详细野外地质调查破裂数据为约束 ,反演了破裂断层面上的同震滑动分布。结果表明 ,破裂下界深度为 1 4 .2～ 2 1km(70 %置信区间 ) ,最佳破裂深度 1 7km。虽然在太阳湖段和主破裂带西端的中间区域未观测到地表破裂 ,但反演的结果表明此区域存在 2～ 3m左右的左旋水平走滑 ,与InSAR资料分析得到的结果一致。地表以下的破裂西端止于太阳湖段 ,而东端似乎在地表破裂迹线以东 30km范围内仍存在 1 .5～ 2 .0m的左旋滑动。反演的垂直位移表明断层在东经 93°以西部分大体表现为南盘上升 ,而东经 93°以东部分表现为北盘上升。由大地测量和地表破裂调查得到的地震矩释放为 6 .1× 1 0 2 0 N·m ,与地震波资料的反演结果基本一致。

The co seismic displacement field of the 2001 west of Kunlun Mountain Pass earthquake is obtained through the analysis of GPS data mea￣sured before and after the earthquake and leveling data measured in 1979 and 2002. Adopting these data, constrained by detail surface rupture data mea￣sured after the earthquake, we inverted the co seismic slip distribution along the seismic fault. The result shows that the depth of rupture lower limit is 14.2～21km (with 70% confidence level), with 17km as the optimal value. The result also shows that left lateral strike slip of 2～3m exists in the area between the Sun Lake segment and the west end of the main rupture zone, although surface rupture is not observed there. This is consistent with the result of InSAR data analysis. The subsurface rupture of this earthquake is ended at the Sun Lake in the west, but it seems that left lateral slip of 1.5～ 2.0m still exists within the range of 30km to the east of the surface rupture zone. The vertical displacement inverted in this study shows that to the west of 93°E the southern side of the fault is eleva￣ted, while to the east of 93°E the northern side of the fault is elevated. The released seismic moment estimated by geodetic data and surface rupture surveying is 6.1×10 20 N ·m, consistent with the result inverted by seismic wave records.