Phases of earthquake's preparation and by chance test of seismic quiescence anomaly

A recently proposed predictive parameter of region-time-length (RTL) was tested using the seismological catalogues of Kamchatka (Russia) and Japan Meteorological Agency (JMA). We introduced the RTL algorithm and summarized the main results of the seismicity variations before the strong earthquakes in Kamchatka. We also investigated the seismicity pattern changes before the disastrous 1995 Kobe earthquake with M=7.2. It was found that a significant seismic quiescence had taken place one year before this event and it had been followed by seven months foreshock activation period. The detailed investigation indicated that the number of clusters of weak earthquakes increased comparatively to the background events during the stages of foreshock activation in the epicenter area of the Kobe earthquake. The by chance test based on randomized earthquake catalogues indicated that the quiescence anomaly in 1994 is a significant one. The results strengthen the physical basis of intermediate-term prediction for large earthquakes. (C) 2002 Elsevier Science Ltd. All rights reserved.