Characteristics of Fault Fracture Zones of the Activated Shionohira Fault and the Non-Activated Kuruma Fault of the 2011 Fukushima-ken Hamadori Earthquake, Northeast Japan

Abstract

Co-seismic surface ruptures in the Fukushima-ken Hamadori Earthquake of Mw 6.7 on April 11, 2011 exposed approximately 14 km trending NNW-SSE from Nameishi to northwest of Ishizumi Tsunaki of Tabito Town, Iwaki City and were newly named the Shionohira Fault. However, no surface ruptures appeared along an N-S trending non-activated Kuruma fault extending 5 km south of the Shionohira Fault. Because of the proximity and similar strike, two locations in Shionohira Fault and one location in Kuruma fault were selected as the study area for the fault activity evaluation. The present study reports the results of a series of geological and drilling surveys, core observation, XRD, isotope, and fluid inclusion analyses, and water permeability test. The results obtained from the three locations offer a fundamental data base that can be utilized for fault activity evaluation by summarizing the geological, mineralogical, and fluid property characteristics of fault fracture zone.