Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Niwa, Masakazu; Shimada, Koji; Terusawa, Shuji*; Goto, Akira*; Nishiyama, Nariaki; Nakajima, Toru; Ishihara, Takanori; Hakoiwa, Hiroaki
Island Arc, 33(1), p.e12516_1 - e12516_16, 2024/02
Times Cited Count：0To investigate the geological evidence of near-surface crustal deformations in a high-strain shear zone that has been geodetically identified but not associated with clear tectonic landforms, a fieldwork was conducted in E-W trending southern Kyushu high-strain shear zone, Japan. According to our study, an investigation based on the slip data from minor faults and the occurrences of fracture zones could help to identify a concealed fault that is small in terms of size to record tectonic landforms but can trigger large earthquakes.
Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Fujita, Natsuko; Yokoyama, Tatsunori; Ogita, Yasuhiro; Fukuda, Shoma; Nakajima, Toru; Kagami, Saya; Ogata, Manabu; et al.
JAEA-Review 2023-017, 27 Pages, 2023/10
JAEA-Review-2023-017.pdf:0.94MB
This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2023. The objectives and contents in fiscal year 2023 are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.
Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Ishihara, Takanori; Ogawa, Hiroki; Hakoiwa, Hiroaki; Watanabe, Tsuyoshi; Nishiyama, Nariaki; Yokoyama, Tatsunori; Ogata, Manabu; et al.
JAEA-Research 2023-005, 78 Pages, 2023/10
JAEA-Research-2023-005.pdf:6.51MB
This annual report documents the progress of research and development (R&D) in the 1st fiscal year of the Japan Atomic Energy Agency 4th Medium- and Long-term Plan (fiscal years 2022-2028) to provide the scientific base for assessing geosphere stability for long-term isolation of high-level radioactive waste. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. The current status of R&D activities with previous scientific and technological progress is summarized.
Nishiyama, Nariaki; Kawamura, Makoto; Umeda, Koji*; Niwa, Masakazu
Oyo Chishitsu, 64(3), p.98 - 111, 2023/08
It is important to accumulate research examples on the spatial distribution of dikes under volcanic edifices for risk assessment in volcanic disaster prevention and site selection and safety assessment for the geological disposal of high-level radioactive waste. The topography of volcanoes is considered to represent the location of magma intrusion associated with volcanic activity and its history. In this study, we attempted to determine the predominant orientation of radial dikes and evaluate the central conduit stability based on the distribution, centroid, and area of contour lines comprising the volcanic edifices using GIS-based topographic analysis. As a result of the topographic analysis, the predominant orientation of the dikes was successfully shown for the volcanoes with stable conduits. On the other hand, this analysis was not suitable for determine the predominant orientation of dikes in volcanoes with unstable conduits, thus the applicable range of this analysis is considered to be determined by the conduit stability. In addition, the conduit stability can be evaluated by using the area data of contour polygons, which represents the scope of application to the method for determination of the predominant orientation of dikes. This means that the conduit stability during volcanic activity can be evaluated even for volcanoes of which activity history is not yet known, and that topographic analysis is a useful tool for this purpose. The use of topographic analysis in this study will be expected to provide a new scale for the history of volcanic activity.
Murakami, Hiroaki; Nishiyama, Nariaki; Takeuchi, Ryuji; Iwatsuki, Teruki
Oyo Chishitsu, 64(2), p.60 - 69, 2023/06
In order to confirm the quality control items for borehole closure in radioactive waste disposal projects, in-situ borehole sealing tests using bentonite material were conducted. As a result, the closure performance was successfully demonstrated by comparing the data of water injection tests conducted before and after the installation of the closure material. However, the breakthrough was observed after closing, probably due to high differential pressure applied to the seal section. Thus, it is important to ascertain throughout the entire operation that the borehole is adequately closed. The placement and specifications of the closure material should be determined according to the hydrogeological structure in the borehole. The confirmation items to use bentonite for sealing material are identified to be: to consider swelling and density loss in the borehole; to place the planned depth using appropriate emplacement technique; to be placed without damage to seals when use some backfilling materials, considering effect of permeability on adjacent seals.
Nishiyama, Nariaki; Goto, Akira*; Tsukahara, Yuzuko; Kawamura, Makoto; Umeda, Koji*; Niwa, Masakazu
JAEA-Testing 2022-003, 51 Pages, 2022/09
JAEA-Testing-2022-003.pdf:5.24MB
JAEA-Testing-2022-003-appendix(CD-ROM).zip:1.12MB
Advancement of the evaluation technology of the magma activity range is essential as one of the technical issues related to volcanic and igneous activities in the evaluation of the long-term stability of the geological environment in the geological disposal of high-level radioactive waste. As an effective method, topographical analysis of volcanic edifices is expected to be used to determine the distribution area of dikes. In recent years, the development of computer-based topographic analysis technology has made it possible to simply perform a large volume of work that would otherwise be difficult due to the manual handling. This report describes an analysis method for the shape of contour lines that forms volcanic edifices using GIS software.
Murakami, Hiroaki; Iwatsuki, Teruki; Takeuchi, Ryuji; Nishiyama, Nariaki*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.22 - 33, 2020/06
Geological disposal of radioactive waste requires the large amounts of fundamental technical knowledge throughout the project. Monitoring is carried out to collect site-relevant information for the creation of an environmental database, to assist in the decision-making process, etc. We summarized the current technical level and problems of the groundwater monitoring in the world. Through the research and technology development so far, the technologies have been developed for drilling borehole in the geological environment survey prior to monitoring and the selection of the monitoring site. However, the following technical developments are remaining issues: long-term operation method of monitoring equipment, retrieving method of monitoring equipment after long-term operation, transport method of backfill material for borehole sealing, technical basis for the sealing performance when the borehole-protective casing and strainer tube are left.
Murakami, Hiroaki; Nishiyama, Nariaki*; Iwatsuki, Teruki; Takeuchi, Ryuji
no journal, ,
no abstracts in English
Murakami, Hiroaki; Nishiyama, Nariaki*; Iwatsuki, Teruki; Takeuchi, Ryuji
no journal, ,
no abstracts in English
Nishiyama, Nariaki*; Takeuchi, Ryuji; Iwatsuki, Teruki; Murakami, Hiroaki
no journal, ,
no abstracts in English
Nishiyama, Nariaki*; Kawamura, Makoto; Umeda, Koji*; Goto, Akira; Niwa, Masakazu
no journal, ,
The authors assume that the topography of the mountain body reflects the actual distribution area of the dike, and we are developing a method to do the model the distribution area of the center conduit and radial dikes by topographical analysis of the mountain body using GIS software. In this study, we proposed a method that enables topographical analysis volcanoes whose activity history is not clear, conducted topographical analysis at each volcano, and modeled the distribution area of dikes. As a result, the analysis method used in this study made it possible to capture the features of the topography formed by the activity of the volcano without including the expert judgement. This makes it possible to compare the analysis results of this study with the geology, and this analysis results are considered to be useful information. In addition, the distribution tendency of the centroid of each altitude obtained in this study shows the results consistent with the wide-area stress field at the time of the eruption, and shows the validity of the analysis results.
Ogata, Manabu; Tsukahara, Yuzuko; Kawamura, Makoto; Kanno, Mizuho; Nishiyama, Nariaki*; Sueoka, Shigeru; Komatsu, Tetsuya; Nakanishi, Toshimichi*; Yasue, Kenichi*
no journal, ,
Optically stimulated luminescence (OSL) dating method on feldspar is useful to date sediments on geomorphological time scale. In this presentation, we present the case studies for marine terraces in the Noto Peninsula and abandoned river valleys along the Oi River, for which the emergence ages were estimated by using feldspar OSL dating. This study was carried out as a part of the establishment of advanced technology for estimation of uplift rates using emergence ages of emergent landforms project.
Nishiyama, Nariaki*; Kawamura, Makoto; Umeda, Koji*; Goto, Akira; Niwa, Masakazu
no journal, ,
The topography of the volcanic mountain body is thought to reflect the actual distribution range of the dike. Based on this idea, we examined the modeling of the dike distribution and the evaluation of the central conduit stability focused on the shape of the contour lines. In this study, we drew the line with the maximum distance (long axis) in the contour distribution of each elevation and aggregated the orientation data, in addition to the data obtained from the analysis of Nishiyama et al. (2021). Moreover, we calculated the topographic parameter of each volcano, using the area data of the area enclosed by the contour lines (contour polygons). As a result, we found that the orientation of the long axis of the contour polygons of volcanic bodies shows the orientation trend in each volcano. The orientation of the line connecting the centroid of many volcanoes is consistent with that of the line connecting the centroid, which is roughly consistent with the direction of sigma 1 around the volcanoes. In general, dikes are characterized by extension in the direction of the maximum compression axis, and our topographic analysis results are consistent with this. As for the topographic parameters of each volcano using the area of contour polygons, the result suggests that it is possible to distinguish between volcanoes classified as central conduit stable and unstable by Takahashi (1994). Therefore, the topographic analysis is expected to be used to evaluate the stability of central conduit even for volcanoes whose activity history is not yet known. In the future, we will develop an evaluation method based on the above topographic features, and establish a method for evaluating the central conduit stability and modeling the distribution of dikes by topographic analysis.
Kawamura, Makoto; Nishiyama, Nariaki; Niwa, Masakazu; Umeda, Koji*
no journal, ,
As the efforts of the notation, "examination of the method of estimating the distribution range of the rock veins distributed under the Quaternary volcano body based on the topographical data of the numerical elevation model" and "Collection and organization of dikes from geological maps (database)" was carried out. These studies are expected to be used as basic information for evaluating the direction and range that are likely to be affected by the horizontal movement of magma due to future volcanic and igneous activities.
Tsukahara, Yuzuko; Ogata, Manabu; Kawamura, Makoto; Kanno, Mizuho*; Nishiyama, Nariaki; Sueoka, Shigeru; Nakanishi, Toshimichi*; Komatsu, Tetsuya
no journal, ,
One hundred thousand-year-scale uplift rate of the Japanese mountains is estimated mainly based on the Terrace to Terrace method (TT method; Yoshiyama and Yanagida, 1995). To apply the TT method, it is necessary to identify the pair of the sedimentary terraces of the last glacial period and the one before last glacial period. However, there are many mountains where such terrace pairs are not recognized. Therefore, as an alternative method to the TT method, we suggest the method based on landforms and deposits of incised meandering rivers (for example, Yasue et al., 2014; Ogata et al., 2021). In this presentation, we will report the results of a survey conducted in the middle of the Oi River as part of such research.
Nishiyama, Nariaki; Nakajima, Toru; Goto, Akira*; Hakoiwa, Hiroaki; Sueoka, Shigeru; Shimada, Koji; Niwa, Masakazu
no journal, ,
For some earthquakes of magnitude 6 to 7, the surface earthquake fault is unclear, and it is necessary to establish an evaluation method to understand the active faults that cause such earthquakes. In this study, in the source area of the 1984 western Nagano Prefecture earthquake, where no distinct surface earthquake faults appeared, we estimated the stress field that may have affected the activity of small faults by stress tensor inversion method using striation data of small faults collected by surface exploration, and extracted areas with many small faults consistent with the regional stress field. As a result of the surface survey, we collected data on 321 small faults. Considering the location and number of these small fault data, the study area was divided into 13 areas. As a result of stress tensor inversion method in each area, stress with a maximum compressive stress axis in the NW-SE direction, which is harmonic to the regional stress field in this area, was detected in the area near the upper end of the hidden fault. In these regions, there are relatively many small faults that were displaced by the activity of the hidden fault, and their distribution area is expected to correspond to the damage zone of the hidden fault or a deformation zone that extends over a wider area. Therefore, even when no clear fault displacement topography is recognized, we expect to be able to estimate its distribution and extent of influence by surface exploration. This study was funded by the Ministry of Economy, Trade and Industry (METI), Japan as part of its R&D supporting program titled "Establishment of Advanced Technology for Evaluating the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (JPJ007597) (Fiscal Years 2020-2022)".
Hakoiwa, Hiroaki; Shimada, Koji; Kawamura, Makoto; Nishiyama, Nariaki; Goto, Akira*
no journal, ,
no abstracts in English
Kawamura, Makoto; Jia, H.*; Koizumi, Yukiko*; Nishiyama, Nariaki; Umeda, Koji*
no journal, ,
Using topographical analysis with GIS using 10 m DEM, we created 2 km river crossing lines on each side of the three rivers, Abegawa, Oigawa and Kumanogawa, starting from the estuary and going straight to the course of the river every 3 km. In addition, the geological information of the river transverse line was extracted. When the cross-sectional lines of the three rivers are displayed together, it can be seen that the river bed rises and the undulations increase as it goes upstream. A comparison of the cross-sectional shapes of the three rivers reveals similar trends, with peaks of undulations on both sides of the rivers in the middle to upper reaches located approximately 500-1,500 m from the center of the river. The relative height between bed and peak also tends to be around 200-600 m. The difference in elevation between the peaks on both sides of the river and the river bed increased in the upstream direction, that is, the depth of the valley to the river bed increased in the upstream direction. When the riverbed slope of the river longitudinal created from the riverbed elevation was taken, an inflection points where the slope trend rose from the upstream area was seen in all three rivers regardless of the geology and geological structure. Although the trend of elevation of the riverbed and increase in undulations from the relatively flat landform near the mouth of the river upstream is pseudo, it suggests a temporal process of landform formation due to uplift and denudation from the flat lowland. This will be information that contributes to verification of the validity of future predictions and performance evaluation models that incorporate topographical changes, such as topographical change simulations.
Nishiyama, Nariaki; Nakajima, Toru; Goto, Akira*; Hakoiwa, Hiroaki; Nagata, Mitsuhiro; Shimada, Koji; Niwa, Masakazu
no journal, ,
Earthquakes of magnitude 6-7 class may occur in areas where active faults have not been detected. To reduce earthquake damage, it is important to understand the concealed active fault that generates such earthquakes, but there is little evidence to provide clues to this understanding. In this study, we collected data on striations observed in fractures by geological survey around the source area of the 1984 Western Nagano Earthquake, where the existence of a concealed active fault is known and conducted multiple inverse method. As a result, stress fields similar to the present stress field were detected in minor faults around the known concealed active fault. Some of the minor faults were recognized in Quaternary volcanic rocks, confirming that the minor faults were very recently active. This indicates that these minor faults may be part of the damage zone that develops around the concealed active fault and is expected to provide a clue to understanding a concealed active fault.
Kawamura, Makoto; Nishiyama, Nariaki; Jia, H.*; Koizumi, Yukiko*; Niwa, Masakazu; Umeda, Koji*
no journal, ,
Volcanic dykes were extracted from a geological map of 1/200,000, and location information was converted into GIS data. More than half of the major axis lengths of rock veins are less than 1 km, the distribution of quaternary volcanic dykes exposed on the surface is limited to within 10 km from the quaternary volcano. Regarding the relationship between the quaternary volcano and the dykes older than the quaternary period, it is considered that the relationship is low as a result of examining the relationship such as the distance and the extension direction of the dykes. We also examined the relationship between Neogene-Tertiary volcanic activity and the dykes distributed in the surrounding area. In the case of Ishizuchi Cauldron, it was shown that the maximum distance from the related rock veins was about 5 km. On the other hand, it was found that the dykes of the Kibi Plateau in the Chugoku region are distributed within a range of approximately 15 km from the central point of activity. Comprehensive information gathering as described above and statistical examination using them are useful as basic information for investigating and evaluating the range of influence of magma in the geological disposal.
