活断層調査のためのγ線測定方法の再検討

抄録

Although γ-ray surveys have often been carried out in order to research active faults, clear correspondence of γ-ray intensity to faults has not always been obtained. We examined over again the methods of γ-ray surveys and the following two points came up as important problems.
(a) The hole to set the senser of γ-ray survey meter must be bored in the same radius and depth at each survey point.
(b) Much attention must be payed to the difference of surface materials.
In order to confirm the usefulness of the method in which the above two points are taken into consideration, the γ-ray surveys were carried out along a line across the Himenoyu fault. This fault was formed at the time of North-Izu earthquake in 1930, and its traces are yet clearly found. A clear peak of γ-ray intensity was obtained at the position on the fault.
Next, this method was applied to the Ono fault whose precise position has not yet known, and we estimated the position of the fault by the results of γ-ray surveys.