Abstract
We measured distribution of natural gamma ray in Monzen-machi, Wajima-shi, Ishkawa-ken that was located by the hypocenter of aftershock. The duration of the measurement was from19th to 20th April 2007, The measurement was carried out using car-borne method along the Route 249. However a felt aftershock of the seismic strength above one grade was not observed during the survey, A few number of aftershock, magnitude two grades, were observed. Relationship between fluctuation gamma ray strength and the time each earthquake occurred is not clear. Extraordinary points which strength of Bismas increases rapidly were found in some points using three-radionuclides analysis. It may suggest that the extraordinary points show the location of fissures caused by earthquake. The fault across the prefectural road Nakanoya had found as an earthquake fault, but we could not observe the increase of gamma ray strength on the road, which had been repaired. We need to clarify that the method will be useful for the earthquake disaster mitigation by collecting data the fluctuation gamma ray strength at the fixed point in our future work.
