Space-Time Anomaly Characteristics of Strain Field before the Ms≥7.0 Earthquakes, In Mainland China

Seismologists focus on analyzing and capturing medium and short-term impending anomalies of medium and small earthquakes before large earthquakes. The natural orthogonal expansion method can effectively extract small and medium seismicity anomalies in the epicentral region before large earthquakes, which can improve the prediction of large earthquakes. In this study, the strain range of small earthquakes that occurred in the Chinese mainland before 1980, specifically ten M s ≥ 7.0 earthquakes, were calculated, and the temporal and spatial anomalies of the strain fields before the large earthquakes were extracted. The active faults in each large earthquake area were analyzed to identify the dangerous areas (Epicenter of earthquake) of the large earthquake. In addition, compared with the seismic energy field method, the natural orthogonal expansion method effectively captured the short-term and impending anomalies in the seismic strain field before large earthquakes. The results of this study can have a significant impact on the analysis of anomalies by strain field, and make an outstanding contribution to the study of large earthquake prediction.