異常地震活動の統計的検出法 (1)

抄録

A statistical method of detecting unusual seismic activities has been developed. Stationary and random earthquake occurrence is assumed throughout the present study. The probability for earthquakes of which the number is larger (smaller) than m to occur during a time-interval S when n earthquakes occurred during a preceding interval T is calculated. It turns out that such a probability is expressed by a negative binomial distribution. When this probability is smaller than a given significance level, the occurrence of more (less) than m earthquakes during S can be recognized to be unusual.
The number of observed micro-earthquakes at the Shiraki Microearthquake Observatory, having the same S-P interval, is analysed. An unusual seismic activity is detected 20 days before the occurrence of the Mivoshi Earthauake Swarm of 1970.