ALOS/PALSARデータを用いた2008年中国汶川地震に伴う地殻変動解析

摘要

We study crustal deformation associated with the Mw7.9 Wenchuan, China, earthquake of May 12, 2008 on the basis of ALOS/PALSAR images to estimate slip distribution. In addition to interferograms along the ascending tracks, we use the ScanSAR data along a descending orbit. The ScanSAR-ScanSAR interferogram has high coherence enough to discuss coseismic deformation, which implies up to 80cm range increase on the south side of the Long-Menshan fault. We jointly invert these data and GPS displacements to estimate slip distribution and dip angle of the source fault simultaneously. The optimal dip angle is estimated to be 48 degrees for the combination of three datasets, while 58 degrees for only InSAR ascending data. The maximum slip is 5m for only ascending data, while it exceeds 8m for the combined datasets. This discrepancy may be attributed to the geometry of the source fault to the line-of-sight direction of SAR, suggesting that enough information cannot be retrieved by only ascending images. It is important to note that thrust component is relatively large in the southwestern part, while dextral slip is prevailing in the northeastern part, in the slip distribution obtained from the joint inversion. These characteristics are consistent with those of surface ruptures detected by field surveys.