基于GPS观测数据的汶川地震断层形变反演分析

Wenchuan Earthquake Deformation Fault Inversion and Analysis Based on GPS Observations

通过高精度数据处理方法获取了2008年5月12日汶川地震(Mw=8.0)可靠的同震形变位移,较大形变主要在汶川、青川和北川县,其中最大同震形变不在震源处,而在北川县,水平方向达到2.3m,垂向为0.7m。并进一步采用分布滑动模型,利用弹性半空间均匀位错理论反演得到同震断层滑动分布。研究结果表明,不约束断层滑动特性的反演结果显示汶川地震断层不仅仅是右旋、逆断层,还伴随着少许左旋走滑及正断层变化。其地震矩张量为2.38X1021N.M,基于反演的断层滑动分布正演的区域同震形变场主要变形区域分别在都江堰—汶川县,北川县,青川县等一带,地表最大变形达到东方向4.5m,北方向0.8m,具有极强的右旋走势,均与野外地质调查结果相符合。

The May12th 2008 Wenchuan earthquake （Mw= 8.0） caused many people death and economic lost inSichuan Province. The surface observation data were rapidly obtained using GPS technology by the State Bureau of Surveying and Mapping （SBSM） and China Earthquake Administration （CEA） after the earthquake braking. In this paper, the reliable co-seismic deformation field is derived from GPS measurements using the highly precise data processing method. The larger deformations are in Wenchuan, Qingchuan and Beichuan Counties rather in the epicenter, while the largest magnitude is up to 2.3 m in the horizontal and 0. 7 m in the vertical direction in Beichuan. The co-seismic fault slip distributions are further inverted using the elastic half-space homogeneous model with distributed slip model. The inversion results show that the non-constrained fault slip is most according with the GPS observed co-seismic deformation and the seismic fault is not only right-lateral and thrust slip, but also with a little left-lateral slip and normal slip slide. The moment tensor is about 2.38×1021 N· M and the main forwardly-inverted co-seismic deformations are in Dujianyan-Wenchuan county and also in Beichuan, Qingchuan areas at the greatest deformation of about 4.5m in the east direction and 0.8m in the north direction with a strongly right-lateral characteristic, which are almost consistent with the wide geological survey results.