Application of the Double-difference Relocation Method Combined with Waveform Cross-correlation on the Three Gorges Reservoir Seismicity

In this paper, we use the double difference location method based on waveform cross-correlation algorithm for precise positioning of the Three Gorges Reservoir (TGR) earthquakes and analysis of seismic activity. First, we use the bi-spectrum cross-correlation method to analyze the seismic waveform data of TGR encrypted networks from March, 2009 to December, 2010, and evaluate the quality of waveform cross-correlation analysis. Combined with the waveform cross-correlation of data obtained, we use the double difference method to relocate the earthquake position. The results show that location precision using bi-spectrum verified waveform cross-correlation data is higher than that by using other types of data, and the mean 2 sig-error in EW, NS and UD are 3.2m, 3.9m and 6.2m, respectively. For the relocation of the Three Gorges Reservoir earthquakes, the results show that the micro-earthquakes along the Shenlongxi river in the Badong reservoir area obviously show the characteristics of three linear zones with nearly east-west direction, which is in accordance with the small faults and carbonate strata line of the neo-tectonic period, revealing the reservoir water main along the underground rivers or caves permeated and induced seismic activity.The stronger earthquakes may have resulted from small earthquakes through the active layers.