利用断层自动剖分技术的2008年青海大柴旦Mw6.3级地震InSAR反演研究

Source Parameters of 2008 Qinghai Dachaidan Mw 6.3 Earthquake from InSAR Inversion and Automated Fault Discretization Method

2008-11-10青海大柴旦地区发生了Mw 6.3级地震,其发震断层位于青藏高原东北缘的大柴旦-宗务隆山断裂带。利用欧空局Envisat/ASAR卫星雷达影像数据,采用二通差分干涉技术获得了地震的同震地表形变场,基于1D协方差函数估计InSAR同震形变场的中误差为0.52cm,方差-协方差衰减距离为5.9km。在此基础上,采用弹性半空间矩形位错模型进行断层几何参数反演,并利用断层自动剖分技术确定了地震的最佳同震滑动分布模型。结果表明,该地震的震源机制解为走向107.19°,倾角56.57°,以逆冲为主兼具少量右旋走滑分量;滑动分布主要发生在10～20km深度范围内,最大滑动量为0.51m,释放的能量为4.3×1018 Nm。

On 10th November 2008, a Mw 6.3 earthquake occurred in the Dachaidan region, Qinghai province, whose seismogenic fault is situated in Dachaidan-Zongwulongshan fault zone which is located on the northeastern margin of Qinghai-Tibet Plateau. A coseismic de- formation field of the earthquake is constructed from ESA Envisat/ASAR radar images using 2-pass differential interferometry. The root mean square error of the InSAR coseismic de-formation field is 0.52 cm with a spatial decay distance of 5.9 km, which are estimated using 1D variance-covariance function. The fault geometry is inverted using a rectangle dislocation model in the elastic half-space and the optimal coseismic fault slip model is determined based on the automated fault discretization method using the observed InSAR data. The invertedhan fault with a strike of 107.19° and a dip of 56.57°, which is dominated by thrust move- ment with a little right-lateral strike-slip component. Most of the slip is observed at a depth of 10-20 kin, and the maximal slip is 0.51 m. The inverted geodetic moment is 4.3×10^18 Nm.