著者
田中 和広 石原 朋和
出版者
公益社団法人 東京地学協会
雑誌
地学雑誌 (ISSN:0022135X)
巻号頁・発行日
vol.118, no.3, pp.499-510, 2009-06-25 (Released:2010-03-26)
参考文献数
34
被引用文献数
6 10

The Nabetachiyama Tunnel 9116 m long was excavated in Tokamachi City, Niigata Prefecture and encountered the serious difficulties during excavation. In particular, a 600 m long section in the Matsudai area had experienced difficulties caused by swelling mudstone in the Tertiary Sugawa Formation. A 120 m bore hole long was excavated in the neighborhood of the section and geological and geochemical examinations of sampled cores were carried out to investigate the formation mechanism of the swelling rock mass. Mudstone distributed deeper than 50 m in the bore hole can be correlated to the tunnel troubled section geologically and geochemically. The section is assumed to be composed of mud breccia with mudstone fragments and clayey matrix, which is thought to be generated by hydro-fracturing of mudstone, showing weak strength due to large quantities of clay minerals. A gas pressure of 1.6 MPa thought to be caused by degassing of methane was measured during tunnel construction, which would increase the swelling properties. Mud breccia distributed deeper than 50 m contains a lot of Na-smectite formed in highly saline pore water ascending from deep underground. The result of slaking test showed that mud breccia filled with saline groundwater is characterized by quick slaking and swelling due to the marked contraction of Na-smectite when drying. In summary, the swelling rock mass distributed in the troubled section was formed by the weak rock strength caused by hydro-fracturing and high gaseous pressure generated by degassing. Furthermore, quick slaking caused by repeated wetting and drying was another reason for swelling during excavation.
著者
田中 和広 東田 優記 村上 裕晃
出版者
日本水文科学会
雑誌
日本水文科学会誌 (ISSN:13429612)
巻号頁・発行日
vol.43, no.4, pp.137-150, 2013-11-30 (Released:2014-01-16)
参考文献数
21
被引用文献数
3 5

紀伊半島の中央構造線近傍に湧出する流体は水質,酸素水素同位体比,ヘリウム同位体比などにより,スラブ起源と考えられる有馬型熱水が混入していることが想定される。本研究では地下水や河川水の地化学特性の検討を行うとともに,露頭における地質学的観察結果にもとづき,流体の上昇経路の検討を行った。流体は幅15 km以内に分布するMTLおよびそれに平行な分岐断層に伴われる断層破砕帯に沿って上昇する。その結果,北部の分岐断層からは主に高塩濃度のNaCl型およびCa(HCO3)2型地下水が,南部のMTLからは一部にCl-の溶存量の高い地下水を含むCaSO4型とCa(HCO3)2型地下水が湧出する。流体は,被圧された局所地下水流動系による希釈を受け,河川と断層の交差する箇所で局地的に湧出している。断層破砕帯中のカタクレーサイトや微小割れ目は方解石脈に充填されており,流体は断層破砕帯を上昇する際に,これらにも浸透し,炭酸カルシウムを沈殿させたものと考えられ,その結果,上昇経路は閉塞され,流出箇所の移動を引き起こしたものと考えられる。
著者
村上 裕晃 田中 和広
出版者
公益社団法人 日本地下水学会
雑誌
地下水学会誌 (ISSN:09134182)
巻号頁・発行日
vol.57, no.4, pp.415-433, 2015-11-30 (Released:2016-02-01)
参考文献数
49
被引用文献数
1 3

島根県津和野地域では,塩濃度の高い鉱泉水がガスを伴い自噴している。この鉱泉水とガスについて,湧出箇所と地化学的特徴を調査した。津和野地域の鉱泉水は最大で海水の約半分程度の塩濃度を示す。自噴するガスは二酸化炭素が主成分である。これらの特徴に加え,鉱泉水の水素・酸素同位体比は天水線から外れる組成を示し,希ガス同位体比からマントル由来のヘリウムの混入が示唆される。これらの地化学的特徴と周辺の地質構造から津和野地域の高塩濃度流体の成因を考察すると,津和野地域の高塩濃度流体には地下深部から供給される流体が含まれていると考えられる。しかし,津和野地域の高塩濃度流体に深部流体が含まれているとしても,その寄与量は最大でも4分の1程度である。また,高塩濃度流体の指標となる塩化物イオンのフラックスが活断層周辺で最も高いことから,高塩濃度流体は活断層を主要な水みちとして移動していると推測される。ただし地表付近において,高塩濃度流体は活断層周辺の亀裂も利用していると考えられる。
著者
田中 和広 石原 朋和
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.118, no.3, pp.499-510, 2009-07-07
被引用文献数
5 10

The Nabetachiyama Tunnel 9116 m long was excavated in Tokamachi City, Niigata Prefecture and encountered the serious difficulties during excavation. In particular, a 600 m long section in the Matsudai area had experienced difficulties caused by swelling mudstone in the Tertiary Sugawa Formation. A 120 m bore hole long was excavated in the neighborhood of the section and geological and geochemical examinations of sampled cores were carried out to investigate the formation mechanism of the swelling rock mass. Mudstone distributed deeper than 50 m in the bore hole can be correlated to the tunnel troubled section geologically and geochemically. The section is assumed to be composed of mud breccia with mudstone fragments and clayey matrix, which is thought to be generated by hydro-fracturing of mudstone, showing weak strength due to large quantities of clay minerals. A gas pressure of 1.6 MPa thought to be caused by degassing of methane was measured during tunnel construction, which would increase the swelling properties. Mud breccia distributed deeper than 50 m contains a lot of Na-smectite formed in highly saline pore water ascending from deep underground. The result of slaking test showed that mud breccia filled with saline groundwater is characterized by quick slaking and swelling due to the marked contraction of Na-smectite when drying. In summary, the swelling rock mass distributed in the troubled section was formed by the weak rock strength caused by hydro-fracturing and high gaseous pressure generated by degassing. Furthermore, quick slaking caused by repeated wetting and drying was another reason for swelling during excavation.
著者
新谷 俊一 田中 和広
出版者
日本自然災害学会
雑誌
自然災害科学 (ISSN:02866021)
巻号頁・発行日
vol.24, no.1, pp.49-58, 2005-05-31
参考文献数
11
被引用文献数
15

We found and described two active mud volcanoes (abbr.: MV), i.e., Gamo MV and Murono MV, and one extinct mud volcano (Shosenji MV) in Tokamachi City, Niigata Prefecture. Active MVs are distributed along the wing of an anticline axis. High saline groundwater, inflammable gas and clay less than 2μm in diameter are erupted from both active MVs. Shosenji MV is exposed near the Gamo MV at a road construction site. Horizontal and vertical structures of the extinct mud volcano, consisting of mud breccia and scaly network clay can be observed. The activity of mud volcano is closely related to the formation of swelling mudstone in the Nabedachiyama Tunnel excavated at the depth of 150m under Gamo MV and Shosenji MV.
著者
浜田 好弘 田中 和広 宮田 雄一郎
出版者
公益社団法人 東京地学協会
雑誌
地学雑誌 (ISSN:0022135X)
巻号頁・発行日
vol.118, no.3, pp.408-423, 2009-06-25 (Released:2010-03-26)
参考文献数
38
被引用文献数
9 8

The geology and geochemistry of mud volcanoes in Taiwan was investigated to elucidate the relationship between their distribution and geological structure and the mechanism of ascending fluid migration from deep underground regions caused by abnormal pore water pressure. A detailed geological survey was carried out to describe the geological structure and the stratigraphy of mud volcanoes in the Pliocene Gutingkeng Formation in the Hsiaokunshui area. Groups of several to tens of mud volcanoes are distributed along the anticline axis within an area of 400 m in diameter. Mud volcanoes are classified into three types on the basis of differences in their morphological features (pudding type, crater type and pool type) corresponding to three types of erupted groundwater having different viscosities. As a result of geochemical studies on groundwater that erupted from mud volcanoes, it is shown that the geochemistry of groundwater that erupted from mud volcanoes distributed along the anticline, such as the Hsiaokunshui mud volcanoes, is characterized by lower δ18O ratios and high concentrations of soluble ions compared to those distributed along the Chishan Fault. Also, it is concluded that pressurized groundwater diluted by water produced during the dehydration of clay minerals ascended through the Chishan Fault and along the Hsiaokunshui anticline. On the other hand, on the basis of high δ18O ratios, it is suggested that the groundwater of mud volcanoes along the Chishan Fault was quickly expelled from underground regions deeper than those along the Hsiaokunshui anticline. Also, the groundwater of mud volcanoes along the Hsiaokunshui anticline ascended through a variety of paths from the mud chamber to the ground surface, and consequently various types of mud volcanoes were formed on the ground surface.
著者
新谷 俊一 田中 和広
出版者
公益社団法人 東京地学協会
雑誌
地学雑誌 (ISSN:0022135X)
巻号頁・発行日
vol.118, no.3, pp.340-349, 2009-06-25 (Released:2010-03-26)
参考文献数
20
被引用文献数
12 12

Mud volcanoes are structures formed as a result of the emissions on a land surface or the sea floor of argillaceous material, which is composed of erupting remobilized mud, petroliferous or magmatic gases, and high-salinity water. Recently, large constructions have been planned deep underground besed on the expectation of geological stability. Therefore, it is important to study the origin of erupted mud and groundwater and the depths from which they ascend when evaluating long-term stability. Three active mud volcanoes and a passive mud volcano are found in the Tertiary Shiiya Formation distributed in Tokamachi City, southern part of Niigata Prefecture. Detailed descriptions of the mud volcanoes are provided by Shinya and Tanaka (2005). However, the origin of erupted mud and the formation mechanism of abnormal pore water pressure have not yet been identified. The authors measured the oxygen and hydrogen isotopic ratio of groundwater and vitrinite reflectance of coal fragments separated from erupted mud of an active mud volcano to investigate the origin of erupted mud, particularly the depth of the origin, and the formation mechanism of abnormal pore water pressure. As a result, δ18O and δD values of erupted water are 1.2‰, -5‰ respectively, showing good agreement with those of the Nanatani Formation distributed at a depth of 3400 m in depth in the studied area. Vitrinite reflectance (Ro) shows a bimodal distribution (i.e., 0.3-1.2% and 1.5-1.8%). Ro value of coal fragments sampled from the Shiiya Formation at the outcrop in the studied area are 0.3-0.45%. High Ro (1.5-1.8%) values of coal fragments are obtained in core samples at a depth of 4000 m in the Gimyo SK-1 oil well, which was excavated 2 km NW from the mud volcano. As a result of an investigation of erupted materials at the mud volcano, they were found to have originated at depths of from 3400 m to 4000 m in the studied area. Geothermal temperature of underground at depth of 3400 m to 4000 m in the in the studied area is estimated to be about 120°C to 150°C. Estimated temperature is high enough to cause diagenetic transition from smectite to illite. Transition from smectite to illite results in the release of a large volume of pore water into the sediment. It is concluded that dehydration due to mineral transition might be the major reason for abnormal pore water pressure formation at depths of 3500 m to 4000 m in the study area.
著者
新谷 俊一 田中 和広
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.118, no.3, pp.340-349, 2009-07-07
参考文献数
20
被引用文献数
3 12

&emsp;Mud volcanoes are structures formed as a result of the emissions on a land surface or the sea floor of argillaceous material, which is composed of erupting remobilized mud, petroliferous or magmatic gases, and high-salinity water. Recently, large constructions have been planned deep underground besed on the expectation of geological stability. Therefore, it is important to study the origin of erupted mud and groundwater and the depths from which they ascend when evaluating long-term stability. Three active mud volcanoes and a passive mud volcano are found in the Tertiary Shiiya Formation distributed in Tokamachi City, southern part of Niigata Prefecture. Detailed descriptions of the mud volcanoes are provided by Shinya and Tanaka (2005). However, the origin of erupted mud and the formation mechanism of abnormal pore water pressure have not yet been identified. The authors measured the oxygen and hydrogen isotopic ratio of groundwater and vitrinite reflectance of coal fragments separated from erupted mud of an active mud volcano to investigate the origin of erupted mud, particularly the depth of the origin, and the formation mechanism of abnormal pore water pressure. As a result, &delta;<sup>18</sup>O and &delta;D values of erupted water are 1.2&permil;, -5&permil; respectively, showing good agreement with those of the Nanatani Formation distributed at a depth of 3400 m in depth in the studied area. Vitrinite reflectance (Ro) shows a bimodal distribution (<i>i.e.</i>, 0.3-1.2% and 1.5-1.8%). Ro value of coal fragments sampled from the Shiiya Formation at the outcrop in the studied area are 0.3-0.45%. High Ro (1.5-1.8%) values of coal fragments are obtained in core samples at a depth of 4000 m in the Gimyo SK-1 oil well, which was excavated 2 km NW from the mud volcano. As a result of an investigation of erupted materials at the mud volcano, they were found to have originated at depths of from 3400 m to 4000 m in the studied area. Geothermal temperature of underground at depth of 3400 m to 4000 m in the in the studied area is estimated to be about 120&deg;C to 150&deg;C. Estimated temperature is high enough to cause diagenetic transition from smectite to illite. Transition from smectite to illite results in the release of a large volume of pore water into the sediment. It is concluded that dehydration due to mineral transition might be the major reason for abnormal pore water pressure formation at depths of 3500 m to 4000 m in the study area.
著者
大島 洋志 徳永 朋祥 宮島 吉雄 田中 和広 石橋 弘道
出版者
一般社団法人日本応用地質学会
雑誌
応用地質 (ISSN:02867737)
巻号頁・発行日
vol.37, no.4, pp.351-358, 1996-10-10
参考文献数
24
被引用文献数
1 6

Data on various hydrological and geochemical fluctuations caused by the 1995 Hyogo-ken Nanbu Earthquake were accumulated. We reported fluctuations of the relatively shallow groundwater at the Nuruyu area, the Northern Awaji Islands, and those of the deeper one at the regional (about 300km&times;300km) scales. Then, we briefly reviewed the precursory geochemical changes in groundwater.<BR>Groundwater gushed out soon after the earthquake at around the Nuruyu and Nojima-Tokiwa areas, which are situated to the east of the Nojima fault, and then has dried up within the several months. There has been no sign of the recovery of groundwater level in wells one year after the earthquake. The water springing out at the hanging wall side along the Nojima fault seemed to be moved from the eastern mountainous area where groundwater has dried up.<BR>Groundwater in deep underground also fluctuated by the earthquake and their spatial distribution seemed to be related to the distance and the direction from the epicenter of the earthquake. Temperature increase at several hot springs has also been observed after the earthquake.<BR>The investigation of the groundwater fluctuations is important not only for the prediction of earthquakes but also for the engineering geological activities, such as planning water supply for the mountainous villages, monitoring and solving groundwater pollution problems, and evaluating long-term stability of deep underground environments. We proposed several plans to monitor and manage data on groundwater fluctuations both in usual times and at earthquakes. We also showed the recommended countermeasure for the fluctuations of hot springs, and pointed out the importance to prepare water supply plans for the places where the drops of water levels have been observed by the previous earthquakes.