Estimation of kinematic and stress history by composite planar fabric and stress inversion analysis: Application to the Shionohira and Kuruma Faults

Sakai, Toru*; Kametaka, Masao*; Aoki, Kazuhiro; Shimada, Koji; Takagi, Hideo*

Chishitsugaku Zasshi (Internet), 130(1), p.89 - 109, 2024/04

https://www.jstage.jst.go.jp/article/geosoc/130/1/130_2024.0001/_article/-char/ja

Shear planes are formed in various orientations within fault fracture zones. The sense of shear on each shear plane can be determined from the composite planar fabrics developed around it. However, it is not possible to distinguish whether all the shear planes in a fault fracture zone were formed during the same stage of motion by observations alone, because of the scarcity of chronological data. As such, we attempted to determine the kinematic and stress histories of the Shionohira and Kuruma faults by using both observations of composite planar fabrics and stress inversion analysis. As a result, we identified five stages of motion on the Shionohira Fault and two stages of motion on the Kuruma Fault. The chronological data are not sufficient to constrain the timing of the stages, but the reconstructed histories are consistent with the paleostress fields and tectonic activity around these faults, as determined in previous studies. Although the reconstructed stress history depends on the density of fault-slip data from the measurement area, this method is effective for investigating the formation mechanisms of fault fracture zones.

Characterizing the reactivation mechanisms of coseismic surface ruptures associated with the 2011 Mw 6.7 Fukushima-ken Hamadori earthquake in Japan through borehole hydromechanical testing

Guglielmi, Y.*; Aoki, Kazuhiro; Cook, P.*; Soom, F.*; Cappa, F.*; Tanaka, Yukumo

Tectonophysics, 819, p.229084_1 - 229084_22, 2021/11

https://doi.org/10.1016/j.tecto.2021.229084

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.

Characteristics of fault fracture zones of the activated Shionohira Fault and the non-activated Kuruma Fault of the 2011 Fukushima-ken Hamadori Earthquake, Northeast Japan

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.

Fine-structure analysis of perhydropolysilazane-derived nano layers in deep-buried condition using polarized neutron reflectometry

Akutsu, Kazuhiro*; Kira, Hiroshi*; Miyata, Noboru*; Hanashima, Takayasu*; Miyazaki, Tsukasa*; Kasai, Satoshi*; Yamazaki, Dai; Soyama, Kazuhiko; Aoki, Hiroyuki

Polymers (Internet), 12(10), p.2180_1 - 2180_10, 2020/10

https://doi.org/10.3390/polym12102180

Examination of evaluation method for fault activity based on morphological observation of fault planes

Tanaka, Yoshihiro*; Kametaka, Masao*; Okazaki, Kazuhiko*; Suzuki, Kazushige*; Seshimo, Kazuyoshi; Aoki, Kazuhiro; Shimada, Koji; Watanabe, Takahiro; Nakayama, Kazuhiko

Oyo Chishitsu, 59(1), p.13 - 27, 2018/04

This paper aims to develop a methodology for understanding the fault activity by observing exposed fault planes without covering younger strata. Based on purpose, faults developed in relatively homogeneous rocks such granitic types are investigated as follows; Gosuke Dam upstream outcrop of Gosukebashi Fault and Funasaka-nishi outcrop of Rokkou Fault were selected for the study of an active fault; and K-3 outcrop of Rokkou Houraikyo Fault was chosen for a non-active fault.

Materials for the information security education

Yashiro, Shigeo; Aoki, Kazuhisa; Sato, Tomohiko; Tanji, Kazuhiro

JAEA-Review 2013-038, 123 Pages, 2014/01

JAEA-Review-2013-038.pdf:23.19MB

With the rapid progress of the utilization of Information Technology (IT), IT infrastructure (network environment and information system) became crucial as a lifeline for promoting business. At the same time, changes in the circumstances surrounding the IT infrastructure globalize the threat of cyber attacks and increase the risk of the information security such as unlawful access to an information system, viral infection, an alteration of a website, disclosure of subtlety information, destruction of an information system and so on. Information security measure is an important issue in Japan Atomic Energy Agency (JAEA). In order to protect the information property of JAEA from the threat, Center for Computational Science & e-Systems (CCSE) has been taking triadic measures for information security: (1) to lay down a set of information security rules, (2) to introduce security equipments to backbone network and (3) to provide information security education. This report is a summary of the contents of the information security education by e-learning.

Investigation and research on depth distribution in soil of radionuclides released by the TEPCO Fukushima Dai-ichi Nuclear Power Plant accident

Sato, Haruo; Niizato, Tadafumi; Amano, Kenji; Tanaka, Shingo; Aoki, Kazuhiro

Materials Research Society Symposium Proceedings, Vol.1518, p.277 - 282, 2013/10

https://doi.org/10.1557/opl.2013.393

The accident of the TEPCO Fukushima Dai-ichi Nuclear Power Plant occurred by the 2011 off the Pacific coast of Tohoku Earthquake on 11 March, 2011. It is estimated that 1.2-1.510 Bq for Cs and 1.5-1.610 Bq for I-131 were released until the beginning of April and those radionuclides (RN) were deposited on soil surface and forest etc. widely around Fukushima Pref. This work was carried out as one of the investigations for making the distribution maps of radiation dose rate and soil contaminated by RNs which the MEXT promotes. The Geoslicer investigation on the depth distribution of RNs in soil was carried out after 3 months from the accident. The investigation was conducted at 11 locations in Nihonmatsu City, Kawamata Town and Namie Town, and soil samples of depth 50 cm to 1 m were taken. Both of Cs and Cs were detected in all investigated locations, and Te and Ag were detected only in areas where radiation dose rates are high. At many locations investigated, radiocaesium more than 99% distributed within a depth of 10 cm in soil in the surface layer. On the other hand, RNs tended to distribute to deeper part in soil at locations that are supposed to have been used as farmland than in soil in the surface layer, and radiocaesium more than 99% in soil at locations that are supposed to have been used as farmland also distributed within a depth of around 14 cm. The apparent diffusion coefficients of RNs derived from penetration profiles near the surface layer showed a tendency to be higher in soil at locations that are supposed to have been used as farmland than in soil in the surface layer. The distribution coefficients by a batch method were also obtained for Cs and I, and the relationship between D and K was discussed.

Study on investigation of microbial effects for geological disposal, 2 (Joint research)

Tochigi, Yoshikatsu; Yoshikawa, Hideki; Aoki, Kazuhiro; Yui, Mikazu; Asano, Takahiro*; Honjo, Hideko*; Haginuma, Masashi*; Kawakami, Yasushi*; Suzuki, Kazunori*

JAEA-Research 2008-025, 55 Pages, 2008/03

JAEA-Research-2008-025.pdf:8.55MB

Results of joint research on fiscal year 2006 between Japan Atomic Energy Agency (JAEA) and Institute of Research and Innovative (IRI) titled as "Study on investigation of microbial effects for geological disposal" are described in this report. The objective of this study is to develop a method for estimating microbial effects for barrier performance of geological disposal site. The modeling was performed to examine the effect on the change in groundwater chemistry (mainly by electron acceptors) by microbial metabolism as well as microbial activities. In order to use the data (chemical composition, biomass, etc.) in the MINT code, groundwater was collected from the drilled well prepared for chemical and microbial analyses of groundwater. The well was prepared in observation field near Horonobe Underground Research Center of JAEA in fiscal year 2006. Then, numerical modeling using collected data of groundwater with numerical modeling program code "MINT" considering microbial effects was carried out. The modeling was carried out to evaluate the microbial effect for stability of chemical and microbial composition of groundwater. As the result of the modeling, relatively low microbial effect for groundwater composition was observed in particular for the concentration of dissolved methane, methanogen, sulfur reducing bacteria (SRB) and sulfur ion. The result shows that low redox potential is stable in the well in spite of shallow depth.

Preliminary results of surface-based investigation at the Horonobe url site, Japan

Yamazaki, Shinichi; Fukushima, Tatsuo; Aoki, Kazuhiro

Proceedings of 2nd International Meeting on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, p.59 - 60, 2005/03

Two off-site Underground Research Laboratory (URL) projects, which are mentioned in the

Developing a remote monitoring system using ACROSS in the Horonobe Underground Research Laboratory

Tsukui, Rota; Niizato, Tadafumi; Aoki, Kazuhiro; Fukushima, Tatsuo

Proceedings of 1st International Workshop on Active Monitoring in the Solid Earth Geophysics (IWAM 2004), 0 Pages, 2004/07

Japan Nuclear Cycle Development Institute (JNC) is developing a remote monitoring system using seismic and electromagnetic ACROSS (Accurately Controlled Routinely Operated Signal System) in the Horonobe Underground Research Laboratory (URL). Horonobe URL is devoting to the technology development for the safe geological disposal of high level radioactive wastes over 20 years. The project has been operating since March 2001 in Horonobe-cho, northern Hokkaido, Japan. The target of a remote monitoring system is to monitor the change of geological environment before, during and after the construction of the URL underground facility. Receiver system of seismic ACROSS and source and receiver system of electromagnetic ACROSS will be installed in 2004 fiscal year, while source of seismic ACROSS will be transported from Tono Geoscience Center in 2005.