关键词: D-InSAR, 汶川M_S8.0地震, 地表形变, 干涉

Abstract: We used the radar data from the satellite ALOS/PALSAR of Japan and the differential interferometric synthetic aperture radar(D-InSAR)technology to derive the coseismic displacement field produced by the M_S 8.0 Wenchuan,Sichucan Province,China earthquake on 12 May 2008.Based on processing SAR data of 7 tracks and 112 scenes by the two-pass method,we obtained the interferometric map of 450km×450km covering the causative fault and determined the distribution range of incoherent zones.Proper phase unwrapping was performed to these tracks of continuous and discontinuous phases,yielding digital image of the interferometric displacement field,which is analyzed by displacement contours and the profile across the fault.The result shows that the Wenchuan M_S 8.0 earthquake has produced a vast area of surface deformation along the Yingxiu-Beichuan Fault,primarily concentrated in a near-field range of 100km wide on the both sides of the causative fault.In this field,the 250km-long and 15～35km wide incoherent zone nearby the fault has suffered the largest deformation with surface ruptures,of which the amount is too large to measure by InSAR.The secondary deformed areas are 70km wide on each side of the incoherent zone,where envelope-like fringes are clear,continuous and converging towards the fault,indicative of increasing gradient and amplitude of displacements which exhibit sunk north wall and uplifted south wall in sight line.With respect to the north and south edges of the data track,the maximum subsidence in the north wall is 110～120cm appearing northeast of Wenhcuan and Maoxian,and a big range of descents of 55～60cm occurred nearby the epicenter south of Lixian.The largest uplift 120～135cm in the south wall is present at the epicenter west of Yingxiu,north to Dujiangyan and around Beichuan.The maximum relative displacement between the north and south walls is up to 240cm that appears nearby the epicenter west of Yingxiu and north to Dujiangyan.In the far-field 70km away from the incoherent zones on the both sides of the causative fault,there are sparse fringes indicative of displacements less than 10cm.The profile across the fault indicates a highly variable gradient of deformation with profound heterogeneity near the fault and in its hanging wall,and a relatively uniform deformation in the foot wall.These differences of deformation can be attributed to complicated thrust faulting.Our analysis suggests that the fault rupture of the Wenchuan earthquake is a relative thrust between the two walls of the fault.

Key words: D-InSAR, Wenchuan M_S8.0 earthquake, surface deformation, interferometry