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Tateishi, Ryo*; Shimada, Koji; Iwamori, Akiyuki*; Wada, Shinya*; Seno, Shotaro*; Nagata, Ken*
Chishitsugaku Zasshi (Internet), 128(1), p.63 - 64, 2022/04
The Tsuruga Fault is an active right-lateral strike-slip fault that is about 20 km in length and distributed in the northeast-southwest direction from the eastern part of Tsuruga City to the southern part of Mihama Town, Fukui Prefecture. The Tsuruga fault borders the Jurassic accretionary complex (mixed rock) and the late Cretaceous granite around the Oritodani area in the Shinjo district of Mihama-cho. Lateral bendings of valleys along the fault in this area are clear geomorphological signatures of fault activity. We briefly report newly found multiple fault outcrops at these bending points with photos of them. This research is the result of joint research by Kansai Electric Power Company, University of Toyama, and JAEA.
Iwamori, Akiyuki*; Takagi, Hideo*; Shimada, Koji; Asahi, Nobutaka*; Sugimori, Tatsuji*; Sasaki, Toshinori*; Aiyama, Kotaro*
no journal, ,
no abstracts in English
Iwamori, Akiyuki*; Ogita, Yasuhiro; Shimada, Koji; Tateishi, Ryo*; Takagi, Hideo*; Ota, Toru*; Kanno, Mizuho*; Wada, Shinya*; Ono, Akihiro*; Otsuka, Yoshiharu*
no journal, ,
We investigated the W value, which is an index showing the progress of weathering, for the fault rocks in the Kojak granite distributed in the eastern Wakasa area. The W value represents the contribution due to weathering calculated from the chemical composition, and along with the M value (contribution of the mafic component) and F value (contribution of the felsic component), a triangular diagram of M + F + W = 100% showing trends from protolith to fault rocks (cataclasite or fault gouge) can be drown. We also investigated on the fault at the geological boundary between the Kojaku granite and the Mino-Tamba metabasalt, and on the difference in characteristics from the fault rock in the Kojaku granite. Granite protolith has an F value of 94.2% and W value of 4.9%, and the fault rock sample has an M value of about 3% regardless of whether it is an active fault or an inactive fault. As weathering progresses, the F value decreases and the W value increases. Metabasalt has an M value of 88.2% and a W value of 6.6%, and the cataclasite has an almost constant F value. As weathering progresses, the M value decreases and the W value increases. Some of the F value increases with the increase of the W value, which is consistent with the contamination of granite-origin quartz fragments found in the basaltic fault gouge. As a result of examination, it was confirmed that Na
O and CaO have a great influence on the increase and decrease of the W value.
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.
Seno, Shotaro*; Tateishi, Ryo*; Shimada, Koji; Iwamori, Akiyuki*; Ogawa, Masaya*
no journal, ,
Several new outcrops of the Tsuruga Fault were discovered through field surveys near the fault distribution location using topographical interpretation using 1mDEM. In one outcrop, a layer of gravel is wrapped around a fractured zone of basement rock. From these sediments the K-Ah and the AT were detected through tephra analysis of fine grained portions. From the horizontal spread of the gravel layer at this outcrop and the attitude of the fault line, we determined the lower limit of the sum of multiple displacements for the horizontal component, diagonal slip component, and vertical component. The lower limit of the average displacement rate was calculated by dividing each component by the age of K-Ah. The results revealed that the vertical component is approximately 0.7m per 1000 years, the horizontal component is approximately 1.4m per 1000 years, and the diagonal component is approximately 1.5m per 1000 years.
