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Aoki, Kazuhiro; Tanaka, Yukumo; Yoshida, Takumi; Shimada, Koji; Sakai, Toru*; Kametaka, Masao*; Seshimo, Kazuyoshi
Oyo Chishitsu, 62(2), p.64 - 81, 2021/06
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 active 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.
Aoki, Kazuhiro; Tanaka, Yukumo; Watanabe, Takahiro*; Seshimo, Kazuyoshi
no journal, ,
no abstracts in English
Tateishi, Ryo*; Shimada, Koji; Niwa, Masakazu; Sueoka, Shigeru; Shimizu, Mayuko; Kanno, Mizuho; Ishii, Chikako; Ishimaru, Tsuneari
no journal, ,
The major difference between active faults and inactive faults is the elapsed time after the latest activity, and while active faults are considered to be on the order of 
to 
years, inactive faults are over 
years. Therefore, even if the phenomena caused by fault activity are the same in both cases, the chemical changes that occur during the subsequent rest period of fault activity may differ significantly. In this study, the chemical composition of fault clay was collected by literature values and actual analysis, and the feasibility of discrimination by the chemical composition examined by linear discriminant analysis. According to the 11 elements selected based on the AIC, 45 active fault samples and 51 inactive fault samples were identified with a discrimination rate of 96%. Among the elements, TiO
and PO
tended to be concentrated as the latest activity period was newer. These concentration mechanisms are for future work.
Tateishi, Ryo*; Shimada, Koji; Iwamori, Akiyuki*; Ogita, Yasuhiro; Wada, Shinya*; Kunimatsu, Wataru*; Otsuka, Yoshiharu*
no journal, ,
It has been demonstrated that active faults (strike-slip faults) and non-active faults developed in granitic rocks in Japan can be discriminated with high probability by linear discriminant analysis using chemical compositions of fault gouge samples. Although, the result included that a reverse fault type active fault was discriminated on the inactive fault side. In this study, to confirm whether this result is due to the difference in fault type or the difference in rock body, chemical composition and linear discriminant analysis of the fault gouge of active reverse faults, active strike-slip faults, and non-active faults in the Kojyaku granite were carried out. As a result, the discrimination rate between active and inactive faults was 100% for 13 (chemical) components and 7 components selected by AIC, and 90% for 3 components. This result suggests the possibility that the difference in the granite bodies affected the discrimination more than the difference of their fault type.