Faculty Profiles - WATANABE Naoki

Papers - WATANABE Naoki

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Water geochemistry and quantitative estimation of its potential sources in 15 representative rivers, Sado Island, Niigata Prefecture, Japan Reviewed

Takeshi Saito, Naoki Watanabe

Geochemistry: Exploration, Environment, Analysis 25 ( 2 ) 1 - 10 2025.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Geological Society of London

The contributions of potential sources to river water geochemistry have rarely been studied in Japan. To characterize the geochemistry of river water on Sado Island, Niigata Prefecture, Japan, water sampling and subsequent chemical analyses were conducted during high- and low-water seasons in 15 representative rivers. The contribution rates of potential sources to the water geochemistry were quantitatively estimated using a straightforward method based on the mass budget equation. The contribution of atmospheric inputs as a source of river water cations was relatively high, ranging from 24.9 to 65.9% and averaging 39.2%. Contributions from rock and mineral weathering, namely gypsum and anhydrite dissolution, silicate weathering and carbonate weathering were estimated to be up to 12.7% (average: 5.8%), 6.1–48.3% (average: 27.4%) and 4.1–52.8% (average: 27.6%), respectively. Although the distribution of carbonates was more limited than that of silicates, their contributions were nearly equal because of the large difference in their weathering rates. This indicates that the water geochemistry of the 15 rivers on Sado Island was mainly controlled by atmospheric inputs and silicate and carbonate weathering.

DOI： 10.1144/geochem2024-025

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Large-scale landslides due to saline water plume intrusion - an example of the Okimi landslide in Niigata Prefecture, Japan Reviewed

Naoki WATANABE, Hisanori SATO, Gen FURUYA

Proceedings of Scientific and Expert Conference Geo-Expo 2024, Geotechnical Society of Bosnia and Herzegovina 33 - 39 2024.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Geotechnical Society of Bosnia and Herzegovina

Large-scale landslides with volumes ranging from tens to hundreds of millions of m3 are scattered throughout Niigata Prefecture, Japan. There is no accepted theory, although many researchers have argued about the mechanism of these landslides. Highly concentrated Na-Cl type groundwater (hereafter called "saline water") has often been found in large-scale landslides in Niigata Prefecture. In addition, the observation wells where saline water occurs are sometimes flowing wells. We also pay special attention to the distribution of landslide-prone areas and oil and gas fields in Niigata Prefecture, which generally overlap, and saline water from landslides is originally fossil seawater such as oil-brine based on geochemical characteristics. On the other hand, anomalous high-pressure reservoirs at depths of more than 1,000 m in oil and gas fields have been known since the 1960s and are possible saline water sources. We believe saline water's behavior is key to better understanding the mechanism of large-scale landslides. The Okimi landslide, this research area, is located in the Kamiya area, Joetsu City, western part of Niigata Prefecture, Japan. The aspect of the active body is about 500 m wide and 1,500 m long, with an area of about 70 ha. The bedrock geology is mainly Neogene unconsolidated mudstone. According to previous studies, saline water has been detected in observation wells at the head of this landslide. Since the geological formation containing saline water has a considerably low resistivity value (≤ 2.0 Ωm), the CSMT method is best suited for electromagnetic exploration to visualize the resistivity up to 1,000 m depth. The survey results confirm the existence of a saline water plume rising from a "saline water chamber" located 100 to 300 m below the western side of this landslide to the bottom of this landslide (at a depth of about 30 m). The presence of the saline water plume suggests that the upwelling of saline water from the anomalous high-pressure reservoir (saline water chamber) is closely related to several large-scale landslides.

DOI： 10.35123/geo-expo_2024_4

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Hydrochemical indicators to predict clogging of drainage pipes by slime accumulation Reviewed

Shohei DOBASHI, Takuma HESHIKIRI, Takashi WATANABE, Taisuke MORIOKA, Takashige AOKI, Naoki WATANABE

Journal of the Japan Landslide Society 61 ( 3 ) 84 - 90 2024.5

Numerical Evaluation of the Effect of Drainage Wells on the Stability of the Ichiba No. 1 Landslide During an Mj6.7 Earthquake Reviewed

Fei Cai, Akihiko Wakai, Naoki Watanabe, Gonghui Wang, Gen Furuya

I. Towhata et al. (eds.), Coseismic Landslides, Springer Natural Hazards 573 - 600 2022.11

Retrofitting method for drainage well by replacing liner-plate wall with exterior concrete Reviewed

Takashi WATANABE, Taisuke MORIOKA, Kunihiko KOSAKAI, Naoki WATANABE

Journal of the Japan Landslide Society 59 ( 6 ) 260 - 264 2022.11

Review of monitoring parameters of the kostanjek landslide (Zagreb, Croatia) Reviewed

Martin Krkač, Snježana Mihalić Arbanas, Željko Arbanas, Sanja Bernat, Kristijan Špehar, Naoki Watanabe, Osamu Nagai, Kyoji Sassa, Hideaki Marui, Gen Furuya, Chunxiang Wang, Josip Rubinić, Koji Matsunami

Landslide Science for a Safer Geoenvironment: Volume 2: Methods of Landslide Studies ( 2 ) 637 - 643 2014.1

Water Quality and Isotopic Characteristics of Lagoon Waters in Niigata Prefecture : In Comparison with Zhalong Wetland at Heilongjiang Province in China Reviewed

TIEMUER Adiljiang, KANO Naoki, IMAIZUMI Hiroshi, LI Chong, WATANABE Naoki, ZHENG Yongjie

RADIOISOTOPES 62 ( 7 ) 409 - 421 2013.7

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Radioisotope Association

In order to reveal the quality and isotopic characteristics of lagoon waters in Niigata Prefecture in recent years, the nutrients concentrations of nitrogen (N) and phosphorus (P) as well as oxygen stable isotope ratios(i.e., δ18O) in water samples of Sakata and Toyanogata were measured. Samples were regularly taken at the fixed sampling points from these lagoons, and depth distribution was surveyed at one point in Toyanogata. In addition, δ18O and nutrients concentrations of water samples in Zhalong Wetland at Heilongjiang Province in China were also determined. Consequently, the following matters have been mainly clarified. (1) δ18O values of sample waters in Zhalong Wetland are generally large probably because of the effect of evaporation, whereas those of Sakata lagoon are large which may be due to the biological process such as the activity of plankton. (2) Considering the results of nutrients concentrations, the water quality of lagoon (Sakata and Toyanogata) waters in Niigata Prefecture is better than that of Zhalong Wetland in China.

DOI： 10.3769/radioisotopes.62.409

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Other Link： http://hdl.handle.net/10191/30806

Two integrated models simulating dynamic process of landslide using GIS Reviewed

Chunxiang Wang, Hideaki Marui, Gen Furuya, Naoki Watanabe

Landslide Science and Practice: Spatial Analysis and Modelling 3 389 - 395 2013

Hydrochemical characteristics of groundwaters from the Kostanjek landslide in Croatia Reviewed

Naoki Watanabe, Martin Krkač, Gen Furuya, Chunxiang Wang, Snjezana Mihalić

Proceedings of 2nd Project Workshop on Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods Rijeka (Croatia), 2011 14 - 16 2012.9

Dynamic simulation of landslide and debris flow in the Rječina River valley, Croatia Reviewed

Chunxiang Wang, Hideaki Marui, Gen Furuya, Naoki Watanabe

Proceedings of 2nd Project Workshop on Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods Rijeka (Croatia), 2011 24 - 28 2012.9

A two-step procedure for hazard prediction and assessment of landslide and debris flow Reviewed

Chunxiang Wang, Hideaki Marui, Gen Furuya, Naoki Watanabe

Proceeding of 12th Congress INTERPRAEVENT, Grenoble, France, 2012 397 - 408 2012.4

Characteristics of oxygen stable isotopic ratio in precipitations in Niigata Prefecture, Japan Reviewed

Chong LI, Naoki KANO, Yuichi UENO, Mitsuru HANABUSA, Yurong JIAO, Hiroshi IMAIZUMI, Naoki WATANABE

RADIOISOTOPES 59 ( 2 ) 93 - 102 2010.2

Large-scale Landslides and Overpressured Hydrothermal System in the Niigata Area, Central Japan Reviewed

WATANABE Naoki, SATO Hisanori, FURUYA Gen

J. Geogr. 118 ( 3 ) 543 - 563 2009.7

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Tokyo Geographical Society

High salinity Na-Cl-type geothermal waters have often been found in the anticlinal hilly terrains and landslide-prone areas of Niigata Prefecture by boring to depths of more than 1,000 meters. These fluid pressure gradients are much higher than the hydrostatic pressure gradient and approach the lithostatic pressure gradient with increasing depth. The geothermal waters in the Matsunoyama area, Tokamachi City, have the highest orifice temperature in Niigata Prefecture. Eight geothermal water wells in this area were drilled along the anticlinal axis of a nearby hilltop or higher breast of the Matsunoyama dome and ranged in depth from 170 to 1,170 meters and in temperature from 35 to 95°C. For example, the Takanoyu-1 geothermal water well is only 170 meters in depth but has an orifice temperature of 90°C. These waters show geyser action associated with methane gas, and typically have very high salinity with considerable amounts of chloride. Hydrogen and oxygen isotope values and chloride concentration of approximately 9,000mg/L suggest that the origin of the waters is altered fossil seawater trapped in organic-matter-bearing sedimentary rocks. The temperature and depth of the primary reservoir are estimated to be 139°C and 3,000 to 4,000 meters, respectively, using a Li-Mg geothermometer and the mean geothermal gradient of 30-40°C/km in the Niigata sedimentary basin. Na-Cl-type groundwaters emerged from several landslides located in the Higashi-kubiki and Naka-kubiki areas including the Matsunoyama area. Well loggings were carried out to profile the electric conductivity and hydrochemistry of groundwater in the Utsunomata landslide in the neighborhood of the Matsunoyama area. Profiles in the active landslide mass showed sharp increases of the electric conductivity and the NaCl components at around the depth of the sliding surface. In contrast, no significant variations of the profiles were recognized in the inactive landslide mass. Na-Cl-type groundwaters are formed by mixing deep Na-Cl-type geothermal waters with meteoric groundwaters. These phenomena suggest that the geothermal water injection into shallow aquifers in landslide mass generates a partially high pore water pressure around the sliding surface and causes landslides.

DOI： 10.5026/jgeography.118.543

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Other Link： https://jlc.jst.go.jp/DN/JALC/00334913632?from=CiNii

Hydrochemical characteristics of groundwaters in the Gosen-Muramatsu Basin, Niigata Prefecture Invited

Annual report of the Institute of Environmental Geological Sciences ( 20 ) 53 - 63 2009.3

Middle Miocene back-arc volcanism in the Tappi-zaki area, Northeast Japan arc: plagioclase K-Ar age constraints

Watanabe, N, Itaya, T, Ohki, J, Shuto, K

Science Reports of Niigata University (Geology) 24 ( 24 ) 91 - 108 2009.3

Environmental characteristics of lagoon waters in Niigata Prefecture based on oxygen stable isotopic ratio and the concentrations of dissolved materials Reviewed

Lu H, Kano N, Yashima Y, Amano Y, Li C, Imaizumi H, Watanabe N, Zheng Y

RADIOISOTOPES 157 ( 7 ) 405 - 418 2008.7

Chemical Weathering Rates from Watersheds in the Tateyama Caldera, Central Japan Invited Reviewed

Watanabe N, Hizuka T, Cheibany O.E, Marui H

Proceedings of the 11th INTERPRAEVENT Conference in DornBirn, Austria 1 537 - 546 2008.5

五頭山西麓の流域における溶存成分フラックス Invited

渡部直喜, 小林裕美, ウルドゥ・エレミン=シェイバニ

(財)環境地質科学研究所研究年報 ( 19 ) 61 - 70 2008.3

2004年新潟県中越地震と地下水異常・活構造

村山友之, 佐藤早苗, 氏原英敏, 森友紀, 豊島剛志, 渡部直喜, 和田幸永, 小安孝幸, 播磨雄太, 小林健太, 大川直樹, 小泉尚嗣

新潟大学災害復興科学センター年報 1号 155 - 174 2007.7

Depth-wise variation of physical and mechanical properties of mudstone in relation to weathering cases in several landslides in Niigata Prefecture Reviewed

Bhattarai P, Marui H, Tiwari B, Watanabe N, Tuladhar G.R

日本地すべり学会誌 44 ( 2 ) 79 - 89 2007.7

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Landslide Society

In order to study the physical and chemical weathering and their impact on the shear strength of the soil mass, soil samples were collected from different depths ranging from the ground surface to a depth of 15m at two different drainage wells in a Mukohidehara landslide area. These specimens represent the residual soil near the surface, specimen at a depth range of ground water level fluctuation, less weathered specimen from the depth below the ground water level fluctuation, the remolded soil from sliding zone and the specimen below sliding zone. Measurement of Atterberg's limits, particle size analysis, X-ray diffraction analysis, slake durability test and X-ray fluorescence tests were carried out. Drained simple shear tests, and drained ring shear tests were also conducted on those specimens to measure their strength characteristics. Test results showed that fully softened shear strength of the less weathered specimen was very close to the peak shear strength of the specimen from the sliding zone. Test results showed no significant variations of index properties (liquid limit, plasticity index and clay fraction) , mineral compositions and chemical compositions with depth. Residual shear strengths of the specimen also did not vary much with depth. In order to compare these findings with rocks from the other types of formation, specimens were collected from the ground surface, ground water fluctuation zone, less weathered zone and sliding zone of three other landslides sites. The test results on the index properties, shear strength properties, mineralogical analysis, and bulk chemistry, of those landslides were consistent with the findings in Mukohidehara landslide. The test results of this study suggested that physical weathering plays a major role in the reduction of shear strength of mudstone, in comparison to the chemical weathering in the form of mineralogical and chemical alteration. Test results also suggested that physical weathering by slaking and disintegration is significant at ground water fluctuation zone in those mudstone formations.

DOI： 10.3313/jls.44.79

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Other Link： https://jlc.jst.go.jp/DN/JALC/00302015801?from=CiNii

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