Co-seismic displacement observation in decorelate belt along seismic fault of 2008 Wenchuan earthquake

摘要

In this work we employ the pixel offset tracking technique to capture large displacements in incoherent zone nearby the Yingxiu-Beichuan fault caused by 2008 Wenchuan Ms8.0 earthquake. The used data of 6 tracks is from ALOS/PASAR dataset of Japan. The result shows that the entire surface rupture belt is 238km long, extending almost linearly in a direction NE42°. It is offset left laterally by a NW-striking fault at Xiaoyudong and turns at Gaochuan, where the rupture belt shifts toward south by 5km largely keeping the original trend. In terms of features of rupture traces, the rupture belt can be divided into 5 sections and 3 types. North to rupture belt, surface displacements are 2.95m on average, mostly in 2.0∼3.5m with the maximum 7.0∼9.0m at individual places nearby Beichuan. South to the rupture belt, the average displacement is 1.75m, dominated by 1.0∼2.0m, with 3.0∼4.0m at a few sites. Along the Guanxian-Jiangyou fault, there is a uplift zone in the radar line of sight, which is 66km long, 1.5∼6.0km wide, with vertical displacements about 2m but no observable rupture traces.