2008年10月当雄M_W 6.3级地震断层参数的InSAR反演及其构造意义

Fault parameters of the October 2008 Damxung Mw6.3 earthquake from InSAR inversion and its tectonic implication

2008年10月6日在西藏当雄发生了Mw 6.3地震.我们从一对降轨ENVISAT ASAR资料获得了这次地震的同震位移场,通过同震位移场的反演确定了发震断层参数.并且应用一维变异理论评估了InSAR结果中的误差协方差矩阵,直接用于评价断层反演参数的不确定性水平.结果表明,此次地震发生于羊易盆地东缘的次级断层,走向178°,倾角58°,倾向近正西,以正断层运动为主,兼具少量右旋走滑分量,且资料的误差水平对反演结果的影响不大.这次地震引起震中位置地表下沉至少30 cm,似乎是亚东谷露裂谷带北段的羊易地堑下沉的表现.

An MW6.3 earthquake occurred in Damxung, Tibet, on October 6th, 2008. We determined the fault parameters using a descending coseismic interferogram from ENVISAT ASAR images. In addition, we examined the uncertainties in the InSAR-derived source parameters using the variance-covariance matrix of InSAR data points estimated with a 1-D semivariogram function. The inverted results showed that the earthquake occurred on a secondary fault in the eastern margin of the Yangyi basin, with a strike of 178°, a dip of 58° and dipping to west, which was normal faulting with a little of right-lateral strike slipping. It also appeared that the impact of the measurement errors on the uncertainties in InSAR derived source parameters was limited. This earthquake led to a subsidence of at least 30 cm at the epicenter, implying the Yangyi basin in the northern Yadong-Gulu Rift Belt was subsiding probably.