RECENT SEISMOMETRICAL WORKS IN JAPAN

Abstract

In order to obtain data for conducting research on the earthquake prediction as well as to monitor the seismic activity in and near Japan, seismological networks have been strengthened by many national universities and agencies. Most stations are telemetered to centers where computerized location facilites are installed, and the telemetered records are processed on a real-time or nearly real-time basis. The structure of hypocentral distribution has been made very clear in many parts of Japan by the data obtained from the networks.
Based on the data by the Japan Meteorological Agency, many researches on the seismicity gap and variation in seismic velocity prior to the occurrence of major earthquakes have been made. The seismicity gap appears to be a positive factor to predict the area where a major earthquake Will occur. On the other hand, both positive and negative results were obtained on the temporal variation in seismic velocity. In view of the present accuracy of observations, even the positive cases should be rechecked.