| 講演要旨(和文) | | 津波被災地の浅層地下水利用地帯において、比抵抗モニタリングによる浅層地下水の水質変化の可視化を試みた．2011年7月の初回調査では、浸透した塩水と推定される低比抵抗薄層が地下水面付近に認められた．2011年10月にはこの薄層は消滅するが、地下水面より深部の比抵抗は減少した．2012年2月、3月には地下水面より上部で比抵抗は顕著に増大した．これは飽和度低下、地温低下、塩分減少の相互作用と考えられる．地下水面より下部でも比抵抗増大が認められ、水質回復の兆候と考えられた．しかし測線近傍の調査井では地下水の比抵抗は明瞭な増大傾向を示さない．震災前の水準への水質回復にはまだ樹幹を要すると考えられる． |
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| | 講演要旨(英文) | | The visualization of the groundwater quality change using the resistivity monitoring was tried in the utilization area of shallow groundwater in the tsunami disaster area caused by the 2011 off the Pacific Coast of Tohoku Earthquake. On the investigation first time in July, 2011, the low resistivity thin layer presumed infiltrating salt water was admitted in the vicinity of the groundwater level. The resistivity of the deeper part from the groundwater level decreased though this thin layer disappeared in October, 2011. The resistivity increased remarkably above the groundwater level in February and March, 2012. This is thought to be an interaction of the saturation decrease, the soil temperature decrease, and the salinity decrease. The resistivity increase was admitted under the groundwater level, and it was thought the symptom of the water quality recovery. However, the resistivity of groundwater did not show a plain increasing trend in the observation well around the survey line. It is thought that time is still required for the groundwater quality recovery to the state before the earthquake. |
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