A telemetering observation of microearthquakes started in May 1976, at the Hokuriku Microearthquake Observatory, Disaster Prevention Research Institute, Kyoto University. In this article, seismicity in the Hokuriku area was investigated, using the data by the telemetering observation for 14 months since May 1967, and historical data of large earthquakes.
The microseismicity is high in the areas from Fukui plain to the north-eastern side of Lake Biwa and from west coast of Lake Biwa to Wakasa Bay. On the contrary, microseismicity is relatively low in the areas of Lake Biwa, off-shore of Japan Sea, and the northern part of Gifu and Ishikawa prefectures.
The microseismicity in this area seems to be closely related to large tectonic structures, such as Fukui earthquake fault, Neodani fault, and Yanagase fault. These active faults, in general, form boundaries between seismically active and aseismic areas.
The active areas of microearthquakes at present are almost coincident with those of disastrous earthquakes in the past. In regard to the activities of the past disastrous earthquakes, there seems to be some regularities of occurrence spacially and temporally.
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