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Watanabe, Tsuyoshi; Asamori, Koichi; Shimada, Akiomi; Ogawa, Hiroki; Saiga, Atsushi; Umeda, Koji*
no journal, ,
no abstracts in English
Bateman, K.; Amano, Yuki; Tachi, Yukio
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Fukuda, Shoma*; Sueoka, Shigeru; Kajita, Yuya*; Hasebe, Noriko*; Tamura, Akihiro*; Morishita, Tomoaki*; Tagami, Takahiro*
no journal, ,
no abstracts in English
Goto, Akira; Shimada, Koji; Niwa, Masakazu; Terusawa, Shuji*
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Owing to a nationwide GNSS network installed since mid-1990s, high-strain shear zone with a sinistral strike-slip was identified in southern Kyushu. There have had large earthquakes in this area such as the 1997 Northwestern Kagoshima Earthquake, however, any seismogenic faults associated with these earthquakes or active faults with strike-slip tectonic landforms had not been previously recognized at the surface. Mesoscale fault zones with clayey gouge and cataclasite are rare in the study area (northwestern Kagoshima (22
16 km)). Instead, minor faults cutting bedding planes and deformation structures subparallel to the bedding, suggesting the formation clearly after the accretion of the Shimanto accretionary complex, are commonly observed. Slip directions can be examined from striations along the minor faults. Based on orientation data of these striations, we applied stress tensor inversion techniques to elucidate stress states. Our field survey revealed an occurrence of the E-W trending zone of 
2 km wide showing a stress state consistent with the sinistral high-strain shear zone (NE-SW compression and NW-SE extension). This study can contribute to one of helpful approaches to examine potential future activities of faults (or shear zones) without clear tectonic landforms.
Nakanishi, Toshimichi; Komatsu, Tetsuya; Hongo, Misao*; Noguchi, Marie*; Miyamoto, Tatsuki*; Kimori, Taiga*; Sugai, Toshihiko*
no journal, ,
no abstracts in English
Ogata, Manabu; King, G.*; Herman, F.*; Sueoka, Shigeru; Yamada, Ryuji*; Omura, Kentaro*
no journal, ,
no abstracts in English
Kawamura, Makoto
no journal, ,
To evaluate the hydraulic and mechanical effects associated with seismic and fault activities, a "conceptual model of seismic and fault activities" has been constructed. However, this conceptual model is qualitative with emphasis on versatility and general viewpoints, and numerical data referred to when setting parameters relating to numerical analysis has not been arranged. In this study, we collected and arranged information published by research institutions such as the Japan Meteorological Agency and universities for relatively large earthquakes and fault activities that occurred in the past, and tried to quantify the conceptual model. As a result, a more specific conceptual model could be constructed by combining geophysical methods such as seismic observation, as well as information based on conventional topographic and geological methods.
Hiratsuka, Shinya; Asamori, Koichi; Saiga, Atsushi
no journal, ,
no abstracts in English
Shimada, Koji; Niwa, Masakazu; Takeuchi, Ryuji; Amano, Kenji
no journal, ,
Domain analysis of granite on the basis of fracture orientation in the 100 m scale by means of structural geologic techniques such as stereographic projection, Strike Versus Traverse Distance diagram and Sequential Linked Median (SLIME) plot revealed relationship between distribution of water conducting fractures and fracture orientations. This attempt used fracture data taken from the "-500m access/research gallery-North" of the Mizunami Underground Research Laboratory. Improvement of the SLIME plot based on running median of span 3 shows water conducting fractures are concentrated at domain boundaries. A location of one of the large kinks corresponds to a region of fractures with geochemical high connectivity from deeper parts.
Nagata, Mitsuhiro*; Yokoyama, Tatsunori; Kagami, Saya; Oto, Shigeru*
no journal, ,
no abstracts in English
Sueoka, Shigeru; Kanno, Mizuho; Kawamura, Makoto; Niwa, Masakazu; Iwano, Hideki*; Danhara, Toru*
no journal, ,
no abstracts in English
Francisco, P. C. M.; Tachi, Yukio
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Kawamura, Makoto; Ishimaru, Tsuneari; Niwa, Masakazu; Komatsu, Tetsuya
no journal, ,
Regarding the selection of the suitable geological environment for geological disposal, not only the evaluation of the activity of the natural phenomena that are currently occurring, but also the prediction of the long-term occurrence and transition of natural phenomena beyond tens of thousands of years after disposal, and It is necessary to properly evaluate the impact on geological environmental conditions. In conducting an appropriate impact assessment, an impact assessment model and scenario will be established. In order to ensure their credibility, it is necessary to clarify the validity of their scientific validity based on the results of case studies. We devised an argument diagram and tried to organize the flow of information. As a result, it was possible to clarify the research contents and results information on necessary natural phenomena and geological environmental conditions for the validity of the set issues, and to clarify the flow of results information for constructing conceptual models and scenarios. In addition, we obtained the prospect of objective judgment on the validity of the evaluation scenario constructed based on the conceptual model.
Komatsu, Tetsuya; Ogata, Manabu; Nakanishi, Toshimichi; Kawamura, Makoto
no journal, ,
no abstracts in English
Sasao, Eiji
no journal, ,
Fractures in the crystalline rock can act as the pathways for groundwater flow and mass transport. Therefore, understanding of the fracture distribution is an important subject for the disposal of high-level nuclear waste. In this study the author discusses the investigation method to understand fracture distribution effectively. The author drew vertical scan lines on the sketches along the north, south east and west walls of the ventilation shaft of the Mizunami Underground Research Laboratory, and counts number of fractures intersected. Fracture frequencies of four lines were varied even in a few meters distance. Coefficient of variation was reversely correlated with fracture frequency. This imply that coefficient of variation could be improved by intersection of more fractures by borehole investigation. Declined borehole directed to dominant direction of fracture is effective method to understand fracture distribution.
Sasaki, Yoshito; Niizato, Tadafumi; Ito, Satomi; Watanabe, Takayoshi
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no abstracts in English
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.
Kijima, Yuichi; Yamamoto, Yoichi; Tomita, Yutaka
no journal, ,
The Japan Atomic Energy Agency has been conducting the measurement of radioxenon using the transportable xenon laboratories (TXLs) at Horonobe, Hokkaido and Mutsu, Aomori since 2018, as part of the noble gas joint measurement project with CTBTO, which is aimed at contribution in better understandings of the measurement data obtained at the CTBT International Monitoring System (IMS) Takasaki radionuclide station. The comparison among the measurement results of radioxenons at 3 measuring points (Horonobe, Mutsu and Takasaki) since 2018, and the analyses results by atmospheric transport modelling (ATM) on estimation of emission source of radioxenon detected will be reported.
Matsushi, Yuki*; Komatsu, Tetsuya; Sueoka, Shigeru; Yonaga, Yusuke; Ogawa, Yumi*; Fujita, Natsuko; Kokubu, Yoko
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no abstracts in English
- 10
years in the Japanese IslandsHiura, Yuki; Komatsu, Tetsuya; Sueoka, Shigeru; Kitamura, Yo*; Sanga, Tomoji*
no journal, ,
Distribution map of erosion rates on geological timescales should be prepared to evaluate the long-term stability of geological environments. Previous distribution maps of erosion rates were constructed based on deposition rates in artificial dams on multi-decadal timescales. This study aims to construct a new distribution map of erosion rates on timescales of 10 - 10 years by using reported data derived from terrestrial cosmogenic nuclide (TCN) methods. This study presents the method for constructing the new distribution map of erosion rate and the results of comparing it with the previous one.