Cryptotephra and pollen assemblages of higher marine terrace-forming materials in the northern side of Nanao Bay, Noto Peninsula, Central Japan

Komatsu, Tetsuya; Furusawa, Akira*; Hongo, Misao*; Tsukahara, Yuzuko; Kawamura, Makoto; Nishiyama, Nariaki; Kanno, Mizuho*; Yasue, Kenichi*

Dai Yonki Kenkyu, 65(1), p.1 - 19, 2026/02

https://doi.org/10.4116/jaqua.65.2417

A flight of Pleistocene marine terraces has been identified in the northern side of Nanao Bay, Noto Peninsula. The H1 terrace among these terraces has been considered to be correlated with MIS 13. This study revisited the formation age of the H1 terrace based on cryptotephra and pollen analyses. Aeolian deposits in the terrace-forming material contained some beta quartz grains. Major chemical element compositions of glass inclusions in beta quartz grains detected in the upper part of the deposit almost matched those of Hakkoda 1st-stage pyroclastic flow deposits (Hakkoda-Kokumoto tephra) chronologically positioned in between MIS 19.1 and 18.4. Additionally, pollens of Neogene elements such as genus Metasequoia, which have been extinct in Japan, were detected in both the marine and aeolian deposits of the terrace. These results suggest that the H1 surface was created during an interglacial period before MIS 19.

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2025)

Asamori, Koichi; Sueoka, Shigeru; Komatsu, Tetsuya; Ogata, Manabu; Uchida, Mao; Nishiyama, Nariaki; Tanaka, Kiriha; Kobayashi, Tomoharu; Mitsuguchi, Takehiro; Murakami, Osamu; et al.

JAEA-Review 2025-035, 29 Pages, 2025/10

JAEA-Review-2025-035.pdf:1.12MB

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 2025. The objectives and contents of this research 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.

Organization of research results into GIS dataset in "Establishment of Advanced Technology for Evaluation the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste FY 2018 to 2022"

Ishihara, Takanori; Nishiyama, Nariaki; Kato, Yuri; Shimada, Koji

JAEA-Data/Code 2024-013, 17 Pages, 2024/12

JAEA-Data-Code-2024-013.pdf:2.8MB
JAEA-Data-Code-2024-013-appendix(DVD-ROM).zip:2305.14MB

Japan Atomic Energy Agency and Central Research Institute of Electric Power Industry conducted collaborative research as a part of "Establishment of Advanced Technology for Evaluating the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2018-2022)" under a contract with the Ministry of Economy, Trade and Industry. We conducted case studies of the effects of major natural phenomena (volcanic and igneous activity, deep-seated fluid, earthquakes and faulting, and uplift and erosion) required to be investigated and evaluated in relation to the selection and modeling of geological environments suitable for geological disposal in Japan, by applying techniques based on the latest research in various academic fields. Through these studies, we accumulated the knowledge necessary to solve problems and advanced our investigation and evaluation techniques. For effectively utilization of these achievements, we organized them in a Geographic Information System (GIS) and compiled them into a dataset that can be viewed in QGIS that free GIS software. This report described the procedure for creating this dataset and how to use it. With publishing this dataset, it is expected that not only seamlessly sharing information within each research field become possible, but also facilitating access and utilization of the research results by researchers in other fields and engineers involved in the geological disposal project.

Analysis of the stress field around concealed active fault from minor faults-slip data collected by geological survey; An Example in the 1984 Western Nagano Earthquake region

Nishiyama, Nariaki; Nakajima, Toru; Goto, Akira*; Hakoiwa, Hiroaki; Nagata, Mitsuhiro; Shimada, Koji; Niwa, Masakazu

Earth and Space Science (Internet), 11(6), p.e2023EA003360_1 - e2023EA003360_15, 2024/06

https://doi.org/10.1029/2023EA003360

Earthquakes with magnitudes of 6-7 have been reported even in various active tectonic settings where fault deformation topography have not been detected. Therefore, delineating concealed active faults generating such earthquakes is necessary to reduce earthquake damage; however, few studies exist to provide its clues regarding such faults. The 1984 Western Nagano Earthquake in Japan was a main shock with a magnitude of Mj 6.8 and a depth of 2 km at the source. Solid bedrocks are well-exposed in the earthquake source region; however, no surface rupture have been identified, and the active fault is known to be concealed. In this study, we collected data on striations observed in fractures by geological survey around the source area of the 1984 Western Nagano Earthquake. Using the collected data, the multiple inverse method was used to estimate the stresses that affected the striation formation. Consequently, stresses similar to acting faults in this area were detected in minor faults around the known concealed active fault. This suggests that the minor faults might be part of the damage zone that has been developed around the concealed active fault. Some minor faults were recognized in Quaternary volcanic rocks, confirming that they experienced displacements recently. This study indicates the possibility of detecting concealed active faults in the bedrock by geological survey.

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2023)

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.

Distribution of Quaternary volcanic dike under the edifices and evaluation of central conduit stability by topographic analysis using contour lines

Nishiyama, Nariaki; Kawamura, Makoto; Umeda, Koji*; Niwa, Masakazu

Oyo Chishitsu, 64(3), p.98 - 111, 2023/08

https://doi.org/10.5110/jjseg.64.98

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.

A GIS-based approach for geomorphological analysis of volcanic edifices to estimate latent magma plumbing system (Contract research)

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.

Data collection and predictive analysis of river denudation

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.

Examination of modeling of Quaternary volcanic central conduit and radial dikes by topographic analysis using GIS software

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.

Application of multiple inverse method to minor faults around the concealed active fault; An Example in the 1984 western Nagano earthquake region

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.