The co-seismic Coulomb stress change and expected seismicity rate caused by 14 April 2010 Ms=7.1 Yushu, China, earthquake

Abstract

A moderate and widely felt earthquake of Ms7.1 (Mw6.9) occurred on April 14, 2010 in Yushu district of Qinghai province (China) which destroyed a large number of buildings and killed more than two thousand people. The distribution of the aftershock sequence is sparse, but with relatively large magnitudes (Ms6.3 and Ms5.7 aftershocks were recorded), strong aftershocks are still highly potential to occur in the near future. Therefore, it is critical to delineate areas where potential aftershocks could occur. Based on static stress triggering theory, we calculated the coseismic stress changes induced by the mainshock in Yushu County and its surrounding regions by adopting elastic dislocation theory and a multilayered crustal model. According to the rate- and state-variable friction law, we calculated the expected seismicity rate and probability of occurrences of M ≥ 5.0 earthquake in the next ten years. It is observed that the Coulomb stress changes increase apparently on the segment of the Wudaoliang-Qumalai Fault, the Batang-Luoxu and Dangjiang-Longbao segments of the Ganzi-Yushu Fault and the whole Wulanwula Lake-Yushu Fault. Based on the theory of Coulomb stress triggering, the probability of earthquake occurrence on these faults would increase in the near future. Considering the historical seismicity, the strain accumulation and the Coulomb stress changes, the probability of M ≥ 5 earthquake and M ≥ 6 earthquake occurrence in the entire study area in the next 10 years are 79–87% and 26.7–33.6%, respectively. Actually, a moderate earthquake of Ms5.3 occurred to the northwest of the Nangqian County on June 26, 2011.

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