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The 12 May 2008 Wenchuan Ms8.0 earthquake produced surface displacements along the causative fault,the Yingxiu-Beichuan Fault,which are up to several meters near the fault.Because of the large gradient,satellite synthetic aperture radar(SAR) interferometric data are strongly incoherent;the usual SAR interferometry method does not allow such displacements to be measured.In the present study,we employed another approach,the technique based on pixel offset tracking,to solve this problem.The used image data of six tracks are from the Advanced Land Observing Satellite,Phased Array type L-band Synthetic Aperture Radar(ALOS/PALSAR) dataset of Japan.The results show that the entire surface rupture belt is 238 km long,extending almost linearly in a direction of 42° north-east.It is offset left laterally by a north-west-striking fault at Xiaoyudong,and turns at Gaochuan,where the rupture belt shifts toward the south by 5 km,largely keeping the original trend.In terms of the features of the rupture traces,the rupture belt can be divided into five sections and three types.Among them,the Beichuan-Chaping and Hongkou-Yingxiu sections are relatively complex,with large widths and variable traces along the trend.The Pingtong-Nanba and Qingping-Jingtang sections appear uniform,characterized by straight traces and small widths.West of Yingxiu,the rupture traces are not clear.North of the rupture belt,surface displacements are 2.95 m on average,mostly 2-3.5 m,with 7-9 m the maximum near Beichuan.South of the rupture belt,the average displacement is 1.75 m,dominated by 1-2 m,with 3-4 m at a few sites.In the north,the displacements in the radar line of sight are of subsidence,and in the south,they are uplifted,in accordance with a right-slip motion that moves the northern wall of the fault to the east,and the southern wall to the west,respectively.Along the Guanxian-Jiangyou Fault,there is a uplift zone in the radar line of sight,which is 66 km long,1.5-6 km wide,and has vertical displacements of approximately 2 m,but no observable rupture traces.
The 12 May 2008 Wenchuan Ms8.0 earthquake produced surface displacements along the causative fault, the Yingxiu-Beichuan Fault, which are up to several meters near the fault. Sccause of the large gradient, satellite synthetic aperture radar (SAR) interferometric data are strongly the usual SAR interferometry method does not allow such displacements to be measured in the present study, we employed another approach, the technique based on pixel offset tracking, to solve this problem. The used image data of six tracks are from the Advanced Land Observing Satellite, Phased Array type L-band Synthetic Aperture Radar (ALOS / PALSAR) dataset of Japan. The results show that the entire surface rupture belt is 238 km long, extending almost linearly in a direction of 42 ° north-east. It is offset left laterally by a north-west-striking fault at Xiaoyudong, and turns at Gaochuan, where the rupture belt shifts toward the south by 5 km, largely keeping the original trend.In terms of the features of the rupt ure traces, the rupture belt can be divided into five sections and three types. Among them, the Beichuan-Chaping and Hongkou-Yingxiu sections are relatively complex, with large widths and variable traces along the trend. Pingtong-Nanba and Qingping-Jingtang sections appear uniform, characterized by straight traces and small widths. West of the rupture traces are not clear. North of the rupture belt, surface displacements are 2.95 m on average, mostly 2-3.5 m, with 7-9 m the maximum near Beichuan. South of the rupture belt, the average displacement is 1.75 m, dominated by 1-2 m, with 3-4 m at a few sites. the north, the displacements in the radar line of sight are of subsidence, and in the south, they are uplifted, in accordance with a right-slip motion that moves the northern wall of the fault to the east, and the southern wall to the west, respectively. Along the Guanxian-Jiangyou Fault, there is a uplift zone in the radar line of sight, which is 66 km long, 1.5-6 km wide, and has vertical displa cements of approximately 2 m, but no observable rupture traces.