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

Abstract

Abstract.To understand the generation of the 2008 Wenchuan, 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).

Precursor-Like Anomalies prior to the 2008 Wenchuan Earthquake: A Critical-but-Constructive Review

“…Anomalous Seismicity. Decade-scale quiescence along the Longmenshan fault zone [20,21]; variation of monthly number of earthquakes since 2000 along the Longmenshan fault zone [22]; six-and-half-year-scale gap of seismicity above M L 4.0, disrupted 1 year before the Wenchuan earthquake [23]; five-year-scale PI "hotspots" along the Longmenshan fault zone, and five-year-scale "accelerating seismic release (ASR)" [21,24,25]; five-year-scale preshock increasing activity of intermediate-depth earthquakes [26]; threeyear scale quiescence of seismicity above M L 6.0 [10, 27]; three-year-scale large-range seismicity pattern [28]; one-tothree-year-scale variation of "load-unload response ratio (LURR)" presented by seismicity [29,30]; variation of "modulated earthquakes" 2 years before the Wenchuan earthquake [31]; two-year-scale variation of the homogeneity in seismicity [32]; variation of several statistical parameters of seismicity since the beginning of 2008 [33,34]; half-year-scale seismic activation identified by PI method [35]. Besides, there are also studies on the potential tidal triggering effect which determines the origin time of the earthquake [36], and relation between Earth rotation and microseismicity [37].…”

“…Except a few studies [10, 24,25,35,79,144,145], there are few discussions on the statistical significance of the correlation between the anomalies observed and the earthquake. This is to much extent a problem which needs to be considered seriously in future, because in the test of earthquake forecast/prediction schemes, statistical significance is one of International Journal of Geophysics 5 the key factors in need of consideration.…”

Evaluation of seismogenesis behavior in Himalayan belt using data mining tools for forecasting

“…1 for various spatio-temporal mapping have been found subject to regional tectonic settings reported in [55]. A concentrated effort to study spatial and temporal variations in seismic activity and use them to recognize patterns that precede large earthquakes has been made by scientists to identify precursory patterns [50,52], seismic quiescence [30,36], swarms in seismic activity analyzed by [31,32,83] and seismicity fluctuations [35,37].…”