| 講演要旨(和文) | | 長野市松代地域では1965年の松代群発地震によって,震源域に地割れ帯が生成され,各地で地すべりが発生した.また,地表には多量のCO2ガスを含んだ湧水が生じた.そのため,松代群発地震はCO2を含んだ流体と地殻の相互作用を知るための良いナチュラルアナログであると考えられている.そこで我々はCO2地中貯留のためのサイト選定とCO2地中貯留の環境へのリスク評価の方法を開発するため,長野市松代地区において5つの測線で電気探査調査を行い,深度約60mまでの比抵抗断面を求めた.その結果,第四紀堆積層中にいくつもの低比抵抗体が存在することが確認された.また,得られた断面を1967年に実施した電気探査結果と比較したところ,当時と現在の大局的な比抵抗構造は大きくは異ならないと考察できた.おそらく,第四紀堆積層中にCO2ガスを含んだ地下水の通り道や貯留層となる多くの割れ目が今でも存在すると考えられる. |
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| | 講演要旨(英文) | | In order to develop the technique of site selection and environmental risk assessment in CO2 geological storage, we conducted electrical surveys in the Matsushiro area, Nagano, where a lot of spring water accompanied by CO2 gas was discharged along the crack and landslide caused by the Matsushiro earthquake swarm that mainly occurred from 1965 to 1970. The electrical data were collected and resistivity sections at depths of up to 60 m were obtained along five survey lines. Although the analyzed sections mainly correspond to the thick Quaternary sediments, many conductive zones appeared in high resistivity medium. We compared the sections with the result of electrical surveys which were conducted in 1967 in order to detect the change of hydrogeological structure in this area. The change is small for these forty years. It seems that there are many fractures which formed paths and reservoirs of ground water containing CO2 gas still now. |
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