Characteristics of long-term regional seismicity before the 2008 Wen-Chuan, China, earthquake using pattern informatics and genetic algorithms

To understand the generation of the 2008 Wen-chuan, China earthquake, we developed a strategy to objectively identify possible seismic precursors. Based on the pattern informatics (PI) method, the pattern of seismic anomaly was identified by the aid of genetic algorithms (GA) to be highly similar to the spatial distribution of the Wen-chuan earthquake sequence. We found that smaller earthquakes (M < 4.4) showed a linear relationship of Gutenberg-Richter (G-R) distribution. However, the frequency of the intermediate earthquakes (M ≥ 4.4) showed an uplift. This uplift supports the seismic activation hypothesis developed by Rundle et al. (2000b) and is similar to the case of the 1999 Chi-chi, Taiwan earthquake sequence reported by Chen (2003).