Dynamic Evolvement of Moderate Earthquakes in the Preparation of Strong Earthquakes in East China

Seismicity of the moderate earthquake before and after strong earthquakes with M≥5.0 since 1970 is studied by Frequency-Area Method(namely S-value)proposed by Wen-xuan Du.Then,a phenomenon is found that the anomaly variations of S-value before and after strong earthquakes are characterized by both commonality and individuality.The commonality is that the S-values become high anomalous values or low anomalous ones before strong earthquakes occur and they decrease or increase after strong earthquakes occur.The individuality is that in the seismogenic area of strong earthquakes on land of East China,S-values become high anomalous values before strong earthquakes occur.But in the sea of East China,S-values become low anomalous values before strong earthquakes occur.The study shows that one can make the dynamic tracing of S-value in the seismogenic area in East China and provide criteria for the earthquake prediction.