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| | Abstract | | We have proposed a novel method to apply integrated near surface geophysical investigation in water covered areas. The major components of the method are under-water hybrid surface wave method and under-water DC resistivity method. To certify the method and to examine its field measurement parameters, we conducted a preliminary study in a river stream. As a result, 2D Vs and resistivity structure was clearly delineated up to 40 m below the river bottom. Regretfully, reference information was very limited. We therefore conducted comparative measurements on the same line deployed on a river bed but under the dry condition. Capacitively coupled resistivity survey using OhmMapper, hybrid surface wave surveys including walk-around surface wave method, and GPR were adopted to obtain the reference data. As a result, 2D Vs structure along the survey line was successfully delineated up to 40 m deep, and resistivity structure of the superficial 10 m in depths. Both structures were basically similar to those obtained by the preliminary study or water-covered condition except for the superficial zone about 2 m in depths or above the groundwater level. |
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