山崎断層付近におけるγ線の測定について (その1)

Abstract

A γ-ray survey was carried out around the Yamasaki fault. The results were not so clearlyinterpreted as were made around the Ohbaku fault.An earthquake of magnitude about 4 occurred near the fault on Sept. 30, 1977. On 27 pointsamong the survey lines above mentioned, time variation of γ-ray intensity was examined by 4times of measurements, one of which was before the earthquake and the rest after it. The patternof the variation is similar to that of Chloride ion contents (Yoshioka (7)) in a spring near the fault.This suggests us that the continuous observation might have caught some precursory change ofthe earthquake occurrence. From the middle of Nov. continuous observation was started in theobservation tunnel of crustal movements at Yasutomi. It seems that high values of γ-ray intensityarise about 4 days after the peaks of the numbers of the microearthquakes and explosions near theregion.