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Journal Articles

Discrimination between active and non-active faults based on the chemical composition of fault gouge; An Attempt using linear discriminant analysis

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$$_{2}$$ 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.

Journal Articles

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.

Journal Articles

Provenance analysis using rapid quantification of heavy minerals via EPMA; A Case study in the Horonobe region, Hokkaido, northern Japan

Yonaga, Yusuke; Sano, Naomi*; Amamiya, Hiroki*; Ogita, Yasuhiro; Niwa, Masakazu; Yasue, Kenichi*

Oyo Chishitsu, 62(1), p.2 - 12, 2021/04

Provenance analysis based on quick identification of heavy minerals using an electron probe microanalyzer (EPMA) was applied to samples from Pleistocene sediments in Horonobe region, Hokkaido, where major provenance rocks can be sedimentary and mafic igneous rocks. The concentrations of 16 elements were measured in individual grains to identify the mineral species based on their chemical composition. In addition, microscopic observation of thin sections and gravel composition analysis were conducted to confirm the validity of the quick identification of heavy minerals. These analyses clarify that combinations of several heavy mineral species can be a useful index of provenance rocks from the Soya Hill and Teshio Mountains, and suggest that uplift of the Soya Hill after ca. 1.5 Ma constrained supply of sediments from the Teshio Mountains. On the other hand, minerals uncommon both in the Soya Hill and Teshio Mountains, such as hornblende, are included in the Pleistocene sediments. This suggests that a sediment supply from distant area was also significant, like transportation by the Teshio River. The method for quick identification of heavy minerals using EPMA can provide an information about provenance rocks difficult to identify only by gravel composition analysis.

Journal Articles

Characteristics and formation process of fractures in crystalline rocks in northern Kyushu

Murakami, Hiroaki; Ashizawa, Masaomi*; Tanaka, Kazuhiro*

Oyo Chishitsu, 59(1), p.2 - 12, 2018/04

This study describes the features of fractures and their fillings along with the long-term behavior of their hydrogeological structures in an underground environment based on the results of a geological investigation conducted at an underground facility in northern Kyushu. Fractures were classified into five groups on the basis of fracture orientation: A, B, C, D, and low-angle groups. The genesis of all fractures is the cooling process of granodiorite pluton. Almost all of the water-conducting fractures are included in the B group. Because a number of fracture fillings in the B group are filled by prehnite and crushed fragments of epidote and quartz, the fractures in this group alternated sealing and re-opening. The fracture characteristics in the B group are follow as: accompanying many alteration halos, long trace length, and cutting off other fractures. These results indicate that fractures in the B group have possibly functioned as pathways for groundwater flow in the long term.

Journal Articles

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.

Journal Articles

Consideration of methodology for estimating hydrochemistry based on results of resistivity logging in deep boreholes

Mizuno, Takashi; Iwatsuki, Teruki; Matsuzaki, Tatsuji*

Oyo Chishitsu, 58(3), p.178 - 187, 2017/08

no abstracts in English

Journal Articles

Development of new method for evaluating the mineral distribution and mode; Quantitative image analysis using the elemental maps obtained by the scanning X-ray analytical microscope

Ishibashi, Masayuki; Yuguchi, Takashi*

Oyo Chishitsu, 58(2), p.80 - 93, 2017/06

Mode of granitic rocks is important information for evaluating their formation process, characterizing fracture distribution and understanding mass transfer in the rock matrix. However, previous methods to evaluate the mode of granitic rocks have several issues. Thus, this study provides the new image analysis method (MJPD method) using scanning X-ray analytical microscope for evaluation of mineral distribution and mode including the secondary minerals. The MJPD method can deal with the heterogeneity of elemental distribution in each mineral. For evaluating the applicability of MJPD method, the method was applied to elemental maps of thin sections. As a result, it was found out that the mineral distribution and mode are easily evaluated by MJPD method using the elemental maps measured in approximately 10,000 seconds. In addition, the MJPD method can be potentially applied to the elemental maps obtained by other analytical instrumentation such as EPMA and SEM-EDS.

Journal Articles

Evaluation of fractures in a rock as flow paths around tunnel using ground penetrating radar

Masumoto, Kazuhiko*; Takeuchi, Ryuji

Oyo Chishitsu, 57(4), p.154 - 161, 2016/10

Fractures developing around the tunnel during the excavation result in issues related not only to the mechanical stability of the rock cavern, but also to the groundwater flow paths. In order to estimate the possibility of application of the GPR (Ground Penetration Radar) to estimate the fractures as low paths, the authors conducted the GPR survey along the side wall of 500 m access tunnel of the Mizunami Underground Research Laboratory of JAEA. The results of the profile measurements indicated that water-conductiong fractures were detected as a reflected waves using GPR survay. Furthermore, as the results of fixed-point measurements during the injection of the saline water, it could be indicated to estimate the flow paths of saline water in the fractures, in a non-destructive way, based on spectral analysis in the reflected waveforms of GPR.

Journal Articles

Geological mapping on the shafts and galleries walls on the Mizunami Underground Research Laboratory project

Tsuruta, Tadahiko; Sasao, Eiji

Oyo Chishitsu, 56(6), p.298 - 307, 2016/02

Japan Atomic Agency (JAEA) are performing Mizunami Underground Research Laboratory project (MIU project), which is a broad scientific study of the deep geological environment as a basis of research and development for geological disposal of nuclear wastes. Geological investigations, reflection seismic surveys, borehole drilling, etc., are carried out to understand the distribution and properties of important geological structures (permeable fractures, faults, etc). This report summarizes specifications and data characteristic of geological mapping on the shafts and gallery wall, and describes contributions to developments of geological model based on the results of geological mapping.

Journal Articles

Predictions of transmissivity of fault zones from strength-stress conditions of rocks

Ishii, Eiichi; Matsuoka, Toshiyuki; Saegusa, Hiromitsu; Takeuchi, Ryuji

Nihon Oyo Chishitsu Gakkai Heisei-27-Nendo Kenkyu Happyokai Koen Rombunshu, p.135 - 136, 2015/09

no abstracts in English

Journal Articles

Development of borehole fracture column and spatial distribution of fracture systems; Case study at the Grimsel test site (GTS, Switzerland)

Tsuda, Hidenori

Oyo Chishitsu, 55(5), p.216 - 228, 2014/12

Regarding grouting of geological disposal repository, geological research that shows the site specific existent condition and aggregation form of rock fractures reached ca.1000 m underground, which buried high-level radioactive waste, is necessary, by a limited number of rock boring survey in the earlier stage of the site investigation. And this fundamental problem holds the key to the success and failure of modeling, design and construction of grouting. This paper introduces rock fractures boring column by simulant real boring core, and attempted to overview of fractures perspective intervening and outer space of borings based on the cross-sectional representation of fractures. Using fractures column, each fracture's location, orientation, and those morphological combination forming fractures aggregate zone are shown systematically. In addition, the relationships between rock fractures and geological features, rock grading are shown in parallel.

Journal Articles

Characterization of water conducting fracture and their long-term behavior in deep crystalline rock; A Case study of the Toki granite

Ishibashi, Masayuki; Ando, Tomomi*; Sasao, Eiji; Yuguchi, Takashi; Nishimoto, Shoji*; Yoshida, Hidekazu*

Oyo Chishitsu, 55(4), p.156 - 165, 2014/10

Understanding of long-term history of water-conducting features such as flow-path fractures is key issue to evaluate deep geological environment for geological disposal of high-level radioactive waste (HLW). Thus, we conducted study on the geological features and the long-term behavior of flow-path fractures based on the data obtained at -300m levels in the Mizunami Underground research laboratory (MIU), central Japan. Total 1670 fractures were mapped in underground gallery at the -300m levels. Flow-path fractures occupy about 11% of all fractures. The flow-path fractures are divided into grout filling fractures and low inflow-rate fractures. All of the grout filling fractures is filled with calcite as fracture filling minerals without conspicuous host rock alteration around fractures. The low inflow-rate fractures possessed similar geological character with the sealed fractures which are not acted as flow-path. The geological character of fracture filling and host tock alteration around fractures indicates the history of the formation at the time of intrusion and emplacement of host granite (Stage I), then filling at hydrothermal event (Stage II), and finally opening and elongation during exhumation stage (Stage III). In conclusion, the present flow-path fractures were formed by opening and/or elongation of pre-existed fractures, which were filled at the hydrothermal event, at the time of exhumation.

Journal Articles

Fractures distribution around underground gallery in sedimentary rock area

Nohara, Shintaro*; Nakata, Eiji*; Suenaga, Hiroshi*; Tanaka, Shiro*; Kubota, Kenji*; Oyama, Takahiro*; Kondo, Keiji

Nihon Oyo Chishitsu Gakkai Heisei-25-Nendo Kenkyu Happyokai Koen Rombunshu, p.129 - 130, 2013/10

no abstracts in English

Journal Articles

Airborne radiation monitoring technique; The Current conditions and the future prospects

Sanada, Yukihisa; Torii, Tatsuo

"Higashi Nihon Daishinsaigo No Oyo Chishitsugaku, Aratana Kadai Toshiteno Haikibutsu Shori To Hoshano Osen" Yokoshu, p.28 - 36, 2013/06

The airborne radiation monitoring technique is developing rapidly by the improvement of the pinpointing technology such as the GPS and the spread of GIS technologies. In addition, a technique to measure the wide area in a short time is demanded. Here, we speak the development of the aiborne radiation measurement technology that JAEA performs since a Fukushima Dai-ichi Nuclear Power Plant accident.

Journal Articles

Tephra stratigraphy of Toki Sand and Gravel Formation on the Nenoue highland; Correlation of widespread tephra deposits by major element chemistry of glass inclusions in quartz

Furusawa, Akira*; Yasue, Kenichi; Nakamura, Chisato*; Umeda, Koji

Oyo Chishitsu, 54(1), p.25 - 38, 2013/04

Distinguishing strongly weathered tephras is very difficult because major-element chemistry of volcanic glasses is affected by weathering. On the other hand, it recently became clear that major-element analysis of glass inclusions in quartz and plagioclase is an effective method of investigating strongly weathered tephras. We studied the weathered tephras in the Toki Sand and Gravel Formation (TSG) located on the Nenoue highland, in the hanging wall of the Byobuyama fault. The TSG consists mainly of gravel beds with intercalated clay-sand beds in the lower and middle horizons. Glass inclusions in the quartz occur only in the weathered clay-sand beds. We found that the glass inclusions in the quartz in the middle horizons of the TSG provide the best correlations with those in the Minamidani-1 tephra deposits in the Kinki, Chubu and Shin-etsu Districts.

Journal Articles

Study on evaluation method of potentional geological environmenral changes of "uplift and erosion" for performance assessment on a high level radioactive waste geological disposal system

Kawamura, Makoto; Ebashi, Takeshi; Makino, Hitoshi; Niizato, Tadafumi; Yasue, Kenichi; Inagaki, Manabu; Oi, Takao

Oyo Chishitsu, 51(5), p.229 - 240, 2010/12

Uplift, subsidence, denudation, and sedimentation are phenomena over long-term in a regional scale. It is difficult to ignore the impacts of those phenomena on a disposal system completely in long-term. Therefore, type and extent of the impacts on geological and disposal environmental conditions, and disposal systems need to be evaluated quantitatively in order to develop perturbation scenarios. We have been developing a systematic methodology to develop perturbation scenarios based on the appropriate understanding of those phenomena. The variety of the change of geological environment and evolution pattern of the environment, which are caused by the variation of the uplift, subsidence, denudation, sedimentation phenomena and those rates, are understood by arranging the information in the framework of the thermal-hydrological-mechanical-chemical-geometrical (T-H-M-C-G) system, and the impacts of those environmental change to the performance of the repository system are also examined by using the T-H-M-C-G system. In this study, firstly, the potential changes of the geological environment were identified by examination of possible combinations of the uplift/denudation and subsidence/ sedimentation. The effects of the initial environmental condition are also considered. Geohistorical information and View of Modern analogue theory should be used in this stage. This procedure is essential to set up the scenarios regarding uplift/denudation and subsidence/sedimentation, to clarify the trend and/or range of the change of the geological environmental conditions. Then, the phenomena which give the large impacts to a disposal system were extracted based on the T-H-M-C-G system. By applying the developed framework which deals with the impacts on the HLW disposal system realistic view and builds evaluation scenarios and models based on step wise manner, we acquired the prospect that realistic uplift and denudation scenario could be built to this examination procedure.

Journal Articles

Characteristics of high angle fractures distributed in granite of MIU (Mizunami Underground Research Laboratory)

Tagami, Masahiko; Ishida, Hideaki; Tsuruta, Tadahiko

Nihon Oyo Chishitsu Gakkai Heisei-21-Nendo Kenkyu Happyokai Koen Rombunshu, p.175 - 176, 2009/10

Fractures in crystalline rocks have exerted a big influence on the underground water stream. It is necessary to understand the fracture shape and distribution from the viewpoint of the material transfer and the safety construction in designing the geological disposal facilities of the high-level nuclear waste. In this report, we examined the fracture characteristics along the horizontal tunnel which was named -300m Access/Research gallery in Mizunami Underground Research Laboratory. Spring water that exceeded 1000 liters per minute was confirmed in the horizontal boring investigation along the tunnel before gallery excavation. We considered the fracture formation process and the function as the passage of water.

Journal Articles

Evaluation of the role of fractures as the major water-conducting features in Neogene sedimentary rocks

Funaki, Hironori; Ishii, Eiichi; Tokiwa, Tetsuya

Oyo Chishitsu, 50(4), p.238 - 247, 2009/10

Evaluation of the role of fracture as the major water-conducting feature in sedimentary rocks is indispensable information to carry out the modelling and analysis of the groundwater flow. We conduct core logging, acoustic televiewer logging and fluid electric conductivity logging at a borehole to clarify the relationship between fracture and flow point. As a result, most of the fractures in the Koetoi Formation don't have a function as major water-conducting features, but some of the fractures in the Wakkanai Formation do. The further statistical analysis indicates; (1) fracture interconnectivity in the Koetoi Formation is poor, while that in the Wakkanai Formation exists to some extent, (2) fracture aperture in the Wakkanai Formation tends to be more than that in the Koetoi Formation. These suggest that the Koetoi Formation would be porous medium and the Wakkanai Formation would be stronger in property as fractured medium than the Koetoi Formation.

Journal Articles

Aeromagnetic survey in an area of weak magnetic anomaly and its interpretation

Hasegawa, Ken; Matsuoka, Toshiyuki

Oyo Chishitsu, 50(1), p.2 - 15, 2009/04

We approached the defining of geological structures with an aeromagnetic survey. The target is the low magnetic anomaly area known as the Ryoke belt. The survey specifications were as follows: Aircraft altitude from the surface is 400m, Survey line interval is 400m, Length and number of survey lines are 38km and 95 respectively. The fundamental data processing such as data compilation, diurnal correction and datum correction were done by means of the "equivalent anomaly" method. Final data shows the magnetic anomaly which may be caused by the Toki granite. To make clear the cause of this anomaly, magnetic susceptibility measurement of rock samples of the Toki granite from some boreholes were done. The results of this measurement indicated that the Toki granite is divided into two zones from the view point of magnetic susceptibility, one zone has relatively high magnetic susceptibility (2 $$times$$10$$^{-3}$$ (SI)), another has quite low magnetic susceptibility (5$$times$$10$$^{-5}$$(SI)). Forward modeling using this result gave the 3-D model of the Toki granite which has relatively high magnetic susceptibility, and this model can almost explain the result of the aeromagnetic survey. Final data shows also additional magnetic anomalies, one may be caused by the normal remanent magnetization of the Hachiya and Nakamura formation above the Kani basin, another one way be caused by unknown intrusive rock above the Mino sedimentary complex rock area. Our approach shows that an aeromagnetic survey can be used to define geological structures for low magnetic anomaly areas such as the Ryoke belt.

Journal Articles

Classification of water level fluctuation data in wells using linear regression models and genetic algorithm

Wakamatsu, Naonori*; Watanabe, Kunio*; Takeuchi, Shinji; Saegusa, Hiromitsu

Oyo Chishitsu, 49(3), p.126 - 138, 2008/08

A method to evaluate similarities of water level fluctuation between wells is proposed. Linear regression models with independent variable for meteorological condition such as rainfall and atmospheric pressure etc. are developed, and well similarity is estimated from model parameters (regression coefficients and model fitness) calculated by Genetic Algorism. The method was applied to the twelve wells in Tono area, central Japan. Although groundwater level fluctuation is primarily affected by rainfall and pumping conditions, different geological conditions would cause different types of water level response to the factors. Models using preceding rainfalls and atmospheric pressure and models using water level in other wells suggested that water level fluctuation data of the wells are classified into groups which reflect difference in pressure propagation for rain infiltration among the geological units.

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