中期地震预报研究

This paper proposes that the upper limit of intermediate-term prediction should be extended to about 20 years from several years, and that intermediate-term prediction should be divided into two stages, early-intermediate-term stage (>2-3 years) and late-intermediate stage. The seismicities in both stages are closely related and difficultly distinguished. The earthquake episode, which embodies the up and down of a group of strong earthquakes in about 20 years, is the main object of early-intermediate prediction. The concentrating process of small quakes along some belts and from far-field to near-field 2-3 years before strong earthquake, accompanied by several anomolies in geophysical and geological fields during the process, is the main object of late-intermediate prediction. Some precursors before Nine Strong Earthquakes (Ms≥7) during 1966-1976 are summarily introduced in the paper. Finally, four models of multi-(stress concetration) points, shunting visco-elastic elements, weakening of source inclus