Basara Miyahara

InSAR-derived crustal deformation and fault models of normal faulting earthquake ( M j 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 Mj 7.0 earthquake that occurred on 11 April, 2011. The most concentrated crustal deformation is located ~20 km west of the city of Iwaki, showing displacements away from the satellite with ~2.2 m at the maximum. Clear displacement discontinuities are recognized with an offset of ~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 ~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°). 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.

Small-displacement linear surface ruptures of the 2016 Kumamoto earthquake sequence detected by ALOS-2 SAR interferometry

Abstract We constructed and analyzed the ground surface displacement associated with the 2016 Kumamoto earthquake sequence using satellite radar interferometry images of the Advanced Land Observing Satellite 2. The radar interferogram generally shows elastic deformation caused by the main earthquakes, but many other linear discontinuities showing displacement are also found. Approximately 230 lineaments are identified, some of which coincide with the positions of known active faults, such as the main earthquake faults belonging to the Futagawa and Hinagu fault zones and other minor faults; however, there are much fewer known active faults than lineaments. In each area, the lineaments have a similar direction and displacement to each other; therefore, they can be divided into several groups based on location and major features. Since the direction of the lineaments coincides with that of known active faults or their conjugate faults, the cause of the lineaments must be related to the tectonic stress field of this region. The lineaments are classified into the following two categories: (1) main earthquake faults and their branched subfaults and (2) secondary faults that are not directly related to the main earthquake but whose slip was probably triggered by the main earthquake or aftershocks.Graphical AbstractIdentified linear surface ruptures. Small solid lines show identified linear surface ruptures. Long, narrow orange area shows the InSAR decorrelation zone along the Futagawa fault zone. Small circles and triangles show epicenters from April 14 to April 23, and beach ball diagrams are from JMA (2016a, b). Red lines show surface ruptures identified by field survey (Geological Survey of Japan 2016).

Detection of 2011 off the Pacific Coast of Tohoku Earthquake-Induced Landslide Deformation Using InSAR

Many researchers have reported the landslide triggered by the 2011 off the Pacific coast of Tohoku earthquake. However, these reports are mainly based on field surveys and interpretation of aerial photographs. In this study, we try to detect and analyze earthquake-induced landslide deformations from InSAR (synthetic aperture radar interferometry) images using Advanced Land Observing Satellite (ALOS)/Phased-array L band SAR (PALSAR) data. We explain this method of landslide detection and introduce examples of detected landslides. It is thought that these landslides do not cause serious, rapid damage because they caused only minor displacement. However, continual monitoring of detected landslides using InSAR is important to prepare for possible landslide reactivation caused not only by an earthquake but also by snowmelt and heavy rainfall.