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| | Abstract | | Remarkable surface raptures appeared along the Yunodake-Fujiwara Fault in Iwaki City, Fukushima Prefecture, is estimated to be generated with an earthquake (Mw 6.6) on April 11, 2011 in southeastern Fukushima Prefecture, which occurred one month after the Great East Japan Earthquake (Mw 9.0) on March 11, 2011. We conducted a CSAMT survey to investigate the underground structure of a southern end part of the fault. Six survey lines were arranged perpendicular to the fault's direction (NW-SE), and the transmitter current source, with a 2km length, was set at about 5 km southeastward from the survey area. A 2D inversion was carried out for each survey line using TM-mode apparent resistivity data. As a result, lateral resistivity changes were clearly recognized in the 2D resistivity sections at the locations of the fault. High resistivity zones (10-100ohmm) were detected in the northeast side of the fault, while low resistivity zones (2-10ohmm) were located at the southwest side. On the other hand, a lateral resistivity change was not detected clearly on the southeastern most survey line, where the earthquake fault was not confirmed on the ground surface. |
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