两次大柴旦Mw6.3地震间地表形变的InSAR观测及与同震破裂的联合分析

InSAR Measurement of Surface Deformation between Two Da-Qaidam Mw6.3 Earthquakes and Joint Analysis with Coseismic Rupture

基于2008-11-10、2009-08-28两次大柴旦Mw6.3地震期间的6景Envisat SAR影像,利用小基线集技术提取相应的InSAR地表形变场。结果显示,震中周缘区域未观测到显著的震后形变空间模式,6个特征点区域的形变序列也未显示由快到慢的时变特征。基于震后形变理论对获取的地表形变进行余滑解释,分析两次地震同震破裂的主要参数,建立震时及期间地下断层滑移过程。两次地震分别在不同深度发生破裂且平均滑移量差异较大,前次地震未产生显著的浅层震后余滑。地震区域岩石圈8.2~23.7km深度内在同震阶段的滑移亏损可能以震间无震滑动的形式予以补偿。

Six Envisat SAR images acquired between two Da-Qaidam Mw6.3earthquakes on November10,2008 and August 28,2009 are used to derive the corresponding InSAR surface deformation field usingthe small baseline subset technique.Obvious spatial patterns of postseismic deformation are not observed around the epicentral zone.Also,temporal characteristic of fast to slow are also not found from the deformation series of the six feature points.The derived surface deformation field is interpreted with the afterslip model of postseismic deformation theory,and the main coseismic rupture parameters of two events are then analyzed,followed by the establishment of the subsurface fault slip process during and between the earthquakes.The two events ruptured at different depth intervals with a big difference of average slip,and the first event did not produce significant shallow postseismic afterslip.The slip deficiency of the lithosphere,of 8.2-23.7km around earthquake zone during the coseismic phase,may be compensated in the form of non-earthquake slip during interseismic phase.