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Guglielmi, Y.*; Aoki, Kazuhiro; Cook, P.*; Soom, F.*; Cappa, F.*; Tanaka, Yukumo
Tectonophysics, 819, p.229084_1 - 229084_22, 2021/11
Times Cited Count：1 Percentile：10.87(Geochemistry & Geophysics)The reactivation mechanisms of coseismic surface ruptures associated with the 2011 Mw 6.7 Fukushima-ken Hamadori earthquake in Japan are investigated using in-situ controlled hydraulic injections in subsurface boreholes. Two fault segments were selected for reactivation studies, one across a coseismic rupture, the Shionohira site, and one across a non-coseismically ruptured segment, the Minakami-kita site. A series of water injections in sealed sections of boreholes set across the fault progressively bring the fault to rupture by a step-by-step decrease of the effective normal stress clamping the fault. While the fault is rupturing during these hydraulic stimulations, borehole displacements, fluid pressure and injection flowrate are continuously monitored. Then, the tests were analyzed using fully coupled hydromechanical modeling. The model was calibrated on field data, and a parametric study was conducted to examine the modes of fault reactivation. Coseismic surface rupture of the Shionohira fault showed a pure dilatant slip response to hydraulic tests, while the tectonically un-activated Itozawa fault (South) indicated a complex hybrid response to tests related to both a higher frictional and cohesive strengths of the fault. The analysis of the induced Shionohira slip event showed that it is reasonably modeled as a Coulomb rupture with an eventual dependency of friction on slip velocity, in good accordance with laboratory-derived rate-and-state friction data on the Shinohira gouge samples. In contrast, the Itozawa fault reactivation mechanism appears dominated by tensile failure with limited Coulomb shear failure. Thus, the applied protocol proves to be able to isolate significant differences in fault physical properties and rupture mechanisms between two segments of the same fault system, opening perspectives to better assess near-surface rupture effects, and therefore the safety of structures subject to large earthquakes.
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.
Shimada, Koji; Kametaka, Masao*; Nakayama, Kazuhiko; Seshimo, Kazuyoshi; Tanaka, Yoshihiro; Hayashi, Toshio*; Tanaka, Yukumo; Shimogama, Kota*; Okazaki, Kazuhiko*
Chishitsugaku Zasshi, 119(11), p.727 - 731, 2013/11
Staples for a stapler can be used as a frame of a small oriented sample taken from fragile and scarce fault gouge. The fault gouge was slotted for staples of an insert. Staples are a group of about ten or less ones holding right-angled three small surfaces. Pre-oriented staples set the slot would remove then presented for the SEM observation. Only a knife, some glues and simple equipment are needed for the method in the field or laboratories.
Yasue, Kenichi; Shimada, Koji; Sasaki, Akimichi; Tanaka, Yukumo; Niwa, Masakazu; Ishimaru, Tsuneari; Umeda, Koji; Tateishi, Ryo*; Kosaka, Hideki*
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no abstracts in English
Ishimaru, Tsuneari; Shimada, Koji; Sasaki, Akimichi; Tanaka, Yukumo; Miyazaki, Masashi; Yasue, Kenichi; Niwa, Masakazu; Sueoka, Shigeru; Umeda, Koji; Ikeda, Makinori
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The Nuclear Regulation Authority instructed to develop a further additional research plan regarding the crushed zones on the Monju site against the JAEA on September 25. The JAEA developed a research plan in response to this instruction, and, the stripping investigation with expansion of the area, the additional detailed geographical and geological surveys around the mountains/terrace boundary, and the marine seismic surveys in the coastal waters, were conducted. The fracture zones were grouped into 2 systems called 
-system and 
-system in the on-site investigation. We examined the cross-cutting relationships and displacements of the fracture zones and confirmed that the -system was formed after the -system. From the investigation results so far, similar to the results of the compilation report of April 31, 2010, no clear evidence was observed to support that on-site crushed zones are active faults.
Shimada, Koji; Tateishi, Ryo*; Ishimaru, Tsuneari; Sasaki, Akimichi; Tanaka, Yukumo; Miyazaki, Masashi; Yasue, Kenichi; Niwa, Masakazu; Sueoka, Shigeru; Umeda, Koji; et al.
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Activity evaluation of crush zones encountered in basement rock is an issue of the seismic safety assessment of nuclear plant and geological isolation of radioactive wastes. The selection of crush zone of which has been evaluated should be defined as the latest one by means of turn determination of crush zone activity based on stratigraphic or structural geological method. A lesson from granitic basement rock (Kojaku granite) holding the fast breeder reactor "Monju" is presented. The Kojaku Granite form the oval Tsuruga peninsula (ca. 8km in width) on the southeastern coast of the Sea of Japan and the age is 68.5 plus/minus 0.7Ma (Zircon U-Pb age).1. Stratigraphy-oriented turn determination of crush zone activity. (1.1) Turn determination using cover sediments. (1.2) Turn determination using dyke, mineral and clay vein. 2. Structural-oriented turn determination of crush zone activity.
Sasaki, Akimichi; Yasue, Kenichi; Shimada, Koji; Tateishi, Ryo*; Ishimaru, Tsuneari; Tanaka, Yukumo
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Seshimo, Kazuyoshi; Aoki, Kazuhiro; Tanaka, Yukumo; Niwa, Masakazu; Shimamoto, Toshihiko*; Ma, S.*; Yao, L.*; Kametaka, Masao*
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Seshimo, Kazuyoshi; Tanaka, Yukumo; Shimada, Koji; Watanabe, Takahiro
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Seshimo, Kazuyoshi; Watanabe, Takahiro; Aoki, Kazuhiro; Tanaka, Yukumo; Guqlielmi, Y.*; Cook, P.*
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Kawamura, Sho; Kobayashi, Tetsuya; Tanaka, Yukumo; Kirita, Fumio; Seshimo, Kazuyoshi; Wada, Shigeru
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Aoki, Kazuhiro; Tanaka, Yukumo; Watanabe, Takahiro*; Seshimo, Kazuyoshi
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Watanabe, Takahiro*; Tanaka, Yukumo; Aoki, Kazuhiro; Guglielmi, Y.*; Cook, P.*; Soom, F.*; Wakahama, Hiroshi*; Nojo, Haruka*; Iwasaki, Etsuo*; Kametaka, Masao*; et al.
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Aoki, Kazuhiro; Tanaka, Yukumo; Yoshida, Takumi; Seshimo, Kazuyoshi; Guglielmi, Y.*; Cook, P.*; Soom, F.*
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Kametaka, Masao*; Tanaka, Yumiko*; Iwasaki, Etsuo*; Aoki, Kazuhiro; Tanaka, Yukumo; Yoshida, Takumi; Seshimo, Kazuyoshi
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no abstracts in English
Aoki, Kazuhiro; Wakahama, Hiroshi*; Nojo, Haruka*; Iwasaki, Etsuo*; Kametaka, Masao*; Tanaka, Yukumo; Yoshida, Takumi; Seshimo, Kazuyoshi
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no abstracts in English
