徳島観測所の新旧観測システムの震源決定能力の比較

Abstract

We started obsevation of microearthquakes by smoked drum recorders in December 1974. The observation points were distributed in Tokushima prefecture and their spans were about 30 km.In May 1985, a tetemetory observation system was constructed based on the Earthquake Prediction Program IV.This system is a constituent of the Nankai Network that intends to survey the seismicity of a broader region, namely, the Median Tectonic Line and the Nankai Trough regions. The observation points of this system, including those of other Universities whose data are sent to Tokushima Observatory by the data exchange system, are distributed widely in the eastern part of Shikoku and Kii Channel.We have obtained a similar seismicity map for the narrow area of the old network, though the intervals of the new network are extended considerably.Judging from Gutenberg and Richter's relation, it is verified that we can fully obtain earthquakes with magnitude more than 2.4, occurring in and near the observation network.