Spatial and temporal b-value precursors preceding the 2008 Wenchuan, China, earthquake (Mw = 7.9): implications for earthquake prediction

• Main Authors: Jie Chen, Shoubiao Zhu
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2020-01-01
• Series: Geomatics, Natural Hazards & Risk
• Subjects: b-value variations; spatial and temporal mapping; earthquake prediction; wenchuan earthquake; longmen shan fault zone
• Online Access: http://dx.doi.org/10.1080/19475705.2020.1784297

The sudden and unexpected Wenchuan earthquake (Mw = 7.9) occurred on the Longmen Shan Fault without any definite precursors. Therefore, a new computing strategy of b-values was applied in the study area around the epicenter of the Wenchuan mainshock, which is divided into nine circular sub-regions with a radius of 50 km uniformly distributed in space, ignoring geological structures. Then the temporal mapping of b-values is performed at each sub-region. The simulated results show that, at one sub-region where the Wenchuan shock is located, the b-value increased to ∼1.25 in 2002 and was almost unchanged for over five years until 2007. But, the b-value dropped to ∼0.5 in Nov. 2007 and remained the same for about three months. Then, b-value increased again since March 2008, and on May 12, 2008, the Wenchuan mainshock occurred. Indeed, according to previous results, this pattern of b-variations is a typical precursor for major earthquakes, which has not been discovered by many retrospect studies for the Wenchuan earthquake. Therefore, this study, which may capture subtle precursors on b-variations for major earthquakes, is significant for earthquake prediction and seismic hazard assessment.