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Tateishi, Ryo*; Shimada, Koji; Shimizu, Mayuko; Ueki, Tadamasa*; Niwa, Masakazu; Sueoka, Shigeru; Ishimaru, Tsuneari
Oyo Chishitsu, 62(2), p.104 - 112, 2021/06
We attempted to discriminate between active and non-active faults by linear discriminant analysis using the chemical composition data of fault gouges in Japan, and then examined the elements that represent the difference between them and better discriminants. As a result, the multiple discriminants obtained could discriminate between them with high probability. In addition, the generalization performance of these discriminants is discussed, and the discriminants that can be expected to have high discriminant performance for unknown samples are presented. Also, from the combination of elements common to these discriminants, we narrowed down the number of elements that represent the difference between active and non-active faults to 6, and showed that the combination of TiO
and Sr contributing the most to the discrimination. The method applied in this study is an innovative one that can discriminate the activity by chemical analysis of fault rocks that are universally present in the bedrock.
Katori, Takuma*; Kobayashi, Kenta*; Niwa, Masakazu; Shimizu, Mayuko; Komatsu, Tetsuya; Yasue, Kenichi; Horiuchi, Yasuharu
no journal, ,
We performed structural analyses and XRD, XGT and EPMA analyses of fault rocks of the Byobuyama fault to reconstruct the history of the fault activity at shallow depth, as a case study for improving research technique to reveal the history of active faults. The results show that fault gouge zone along the fault has experienced activities of several stages under different stress, and significant differences in the deformation and alteration mechanism exist between these stages. Especially, the flow deformation of the fault gouge indicates that a large amount of fluid was present during the deformation. Abundance of illite infers that such fault gouge was formed by relatively high temperature fluid. In addition, eluviation structure of albite may indicate a deformation under environment such as to promote reaction solution. In this presentation, we discuss the vicissitudes of deformation and alteration mechanism in the fault gouge along the Byobuyama fault.
Tateishi, Ryo*; Shimada, Koji; Shimizu, Mayuko; Sueoka, Shigeru; Niwa, Masakazu; Ishimaru, Tsuneari
no journal, ,
The identification of active faults is based on the displacement and deformation of the current topography and the late Quaternary strata. However, in the absence of them, it is difficult to determine the fault activity. To solve this problem, multivariate analysis was performed using chemical composition data of fault gouges of active and inactive faults in Japan. We performed linear discriminant analysis with a following combination of elements; (a) 11 elements selected by AIC, (b) 8 elements with p-value between 0 and 0.01, (c) 6 elements with p-value between 0 and 0.001. The discrimination rate between active faults and inactive faults is 100% in (a), (b) and 97% in (c). Among elements that represent the difference, TiO and PO
, and AlO
and Rb are considered important, including their respective combinations. These results contribute to clarify the mechanism that creates the difference in chemical composition between active and inactive faults.
