Abstract
Radon-222 concentrations in groundwater were surveyed along active faults in Miura Peninsula. A mean value of radon concentrations was 5.8±4.8BqL−1, which was slightly higher than a background level of 3±2Bq L−1 in Shonan area, Kanagawa Prefecture. The highest value was 17.2±1.0Bq L−1 at Iwato town, Yokosuka City. A few groundwater samples provided higher values of radon concentration relative to the background. In addition, a radon concentration profile, which was plotted against to a distance between a sampling point and a fault line, showed a low radon concentration zone on the fault line surrounded by high radon concentration zones. Since there is no big river in Miura Peninsula, it is presumed that the high radon concentration zone indicates the existence of fracture zones along active faults.
