| Project/Area Number |
14580505
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Natural disaster science
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| Research Institution | Yamaguchi University |
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Principal Investigator |
TANAKA Kazuhiro Yamaguchi University, Faculty of Science, Professor, 理学部, 教授 (80335760)
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| Co-Investigator(Kenkyū-buntansha) |
CHIGIRA Masahiro Kyoto University, Disaster Prevention Insitute, Professor, 防災研究所, 教授 (00293960)
MIYATA Yuichiro Yamaguchi University, Faculty of Science, Professor, 理学部, 教授 (60253134)
KANAORI Yuji Yamaguchi University, Faculty of Science, Professor, 理学部, 教授 (60194883)
MAHARA Yasunori Kyoto University, Research Reactor Institute, Professor, 原子炉実験所, 教授 (30371537)
OYAMA Takahiro Central Research Institute of Electric Power Industry, Civil Engineering Research Laboratory, Senior Researcher, 地球工学研究所, 上席研究員 (30371404)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | mud volcano / mud diapir / groundwater / swelling rockmass / natural gase / geological survey / geophysical exprolation / CSAMT method / 異常間隙水圧 / 地質構造 / 新第三紀層 / 台湾 |
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| Research Abstract |
Activity of mud volcano is thought to be caused by an abnormal water pressure generated in deep underground and make a serious problem for underground constructions such as railway tunnel, underground facility for radwaste and so on. It is important to investigate the underground structure of a mud volcano and the mechanism of abnormal water formation for site selection and safety assessment of such facilities.
Serious trouble such as tunnel wall collapse due to the rock swelling has happened 180m deep under mud volcanoes. It took more than 10 years to excavate the section of 150m long. 4 terrestrial mud volcanoes were found in the Tertiary sedimentary basin in Niigata, central Japan
All the mud volcanoes are distributed along the rim of the topographic basin that is located at the NE-SW trending crest of mountainous area and distributed along the wing of anticline. Geological structure inside basin is heavily disturbed.
The extinct mud volcano is exposed in the side-slope of newly constr
… More
ucted road and the internal vent structure of mud volcano can be observed. The vent is 30m in diameter and is consisted of mud breccia and scaly network clay that is thought to be generated by hydro-fracturing and the following water-rock interaction between mudstone and groundwater.
Groundwater erupted from mud volcano is highly saline with electric conductivity of 15mS/cm and high ^<18>O/^<16>O isotope ratio of 1.2‰. Also, the vitrinite reflectance is 1.5 to 1.9% that is not expected in the sedimentary rocks exposed near ground surface. As a result, it is assumed that these erupted materials were introduced from the deep underground about 4000m deep.
CSA-MT geophysical exploration was carried out to survey the underground structure and obtained the profile of electrical resistivity from the surface to 800m in depth. It is found that the disk-shaped low resistivity zone less than 1Ωm due to the high salinity content is identified in underground 600m deep, 200m thick and 800m in diameter under the mud volcanoes. Moreover, low resistivity zone is continuing to the ground surface along the rim of the basin structure similar to volcanic caldera where mud volcanoes are active. Less
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