InSAR-derived crustal deformation and fault models of normal faulting earthquake (Mj 7.0) in the Fukushima-Hamadori area

Applying interferometric SAR (InSAR) analysis using ALOS/PALSAR data to inland crustal earthquakes in the Fukushima-Hamadori area, we succeeded in mapping a ground displacement associated with the M-j 7.0 earthquake that occurred on 11 April, 2011. The most concentrated crustal deformation is located similar to 20 km west of the city of Iwaki, showing displacements away from the satellite with similar to 2.2 m at the maximum. Clear displacement discontinuities are recognized with an offset of similar to 1.6 m at the maximum, which are just on the Shionohira, Idosawa and Yunotake faults. From field surveys, we found that earthquake surface faults appeared with a vertical offset of similar to 1.9 m, consistent with the InSAR observation, and their locations correspond to the discontinuities in the interferogram. We inverted the InSAR data to construct slip distribution models, and our models show (1) nearly pure normal fault motions (2) on west-dipping planes (3) with moderate-dip-angles (50-65 degrees). The inferred west-dipping normal fault motion on the Yunotake fault is correlated with the present-day topographic features, consistent with the idea that the historically-repeated normal faultings have developed the topography. On the other hand, for the Shionohira and Idosawa faults antithetical relationships are presented, maybe suggesting that large normal faultings have been infrequent historically.