The 2011 Tohoku earthquake and the related disasters observed by InSAR using ALOS/PALSAR: Mainshock, induced inland earthquakes, and liquefaction

摘要

Applying an interferometric SAR (InSAR) analysis to the 2011 Tohoku earthquake, we succeeded in mapping a ground displacement distributed all over eastern Japan. The InSAR analysis incorporating GNSS data is inevitable to accurately obtain deformation map covering a vast area, even when using precise orbit information. We further detected locally-distributed ground deformation anomalies due to several induced crustal inland earthquakes. For the Fukushima-Hamadori earthquake, clear displacement discontinuities corresponding to earthquake surface faults can be identified in the interferogram, suggesting multiple ruptures occurred under the ground. It demonstrates that an InSAR observation is advantageous for understanding of the complexity of inland earthquakes. We attempted to detect the spatial extent of liquefaction areas using coherence values. We found several coherence reduction areas, where there are good spatial correlations with the actual liquefaction areas observed field surveyes. It suggests that coherence values can be effective to search liquefaction areas exhaustively.