Intersection area of synthetic anomalies of C,D and Mf values── a middle-term anomaly prior to moderately strong earthquakes in East China region

The phenomena show that the activities of moderate and small earthquake usually Indicate a strengthening process prior to large earthquakes and that large earthquakes often occur in the periphery of the anomalous zone. The Intersection area of anomalous zones of the parameters describing the characteristics of the temporal, spatial and intensity distributions of earthquakes (the spatial concentration degree C, the seismic risk degree D and the seismic intensity factor Mf) could be used to predict the epicentral location of the future earthquake. The application of the method to the earthquake prediction in East Chi- na region has shown that the accuracy of the estimated epicentral location might reach 1°- 1. 5° (radius), and false alarms and missed prediction of earthquakes resulted from using only single parameter can be avoided efficiently.