A moderate and widely felt earthquake of MS7.1 occurred on April 14, 2010 in Yushu district of Qinghai province, China. Comparing with typical intraplate earthquakes, the exceptional characteristic of aftershock sequence of Yushu earthquake is that the aftershocks are exceptionally sparse and strong for such a moderate earthquake. Thus, the relationship between the MS7.1 mainshock and its aftershocks should provide us a good opportunity to investigate the mechanism of aftershock occurrences. Based on the elastic dislocation theory and multilayer lithospheric model, we calculate the coseismic static and postseismic viscoelastic relaxation stress changes induced by the Yushu earthquake, analyze its influence on aftershocks distribution, and discuss the interaction between MS7.1 Yushu earthquake and 2011 MS5.2 Nangqên earthquake. The results show that the coseismic stress changes induced by Yushu earthquake obviously raised the stress accumulation in four regions. Analyzing the relationship between Coulomb stress changes and aftershocks distribution, the numerical result is insensitive to the effective coefficient of friction and calculated depth, but more sensitive to the effect of regional stress. Taking the regional stress into account, 86.7% of total aftershocks located in the regions with increased Coulomb stress. The aftershock distribution of Yushu earthquake could be well explained by the earthquake stress triggering theory. Taking the two nodal planes of the focal mechanism of Nangqên earthquake as the receiver fault, we calculate the coseismic and postseismic stress changes with different viscosities. The numerical results indicate that the hypocenter of Nangqên earthquake always locates in the stress shadow, which means the theories of static and viscoelastic relaxation stress triggering can not explain the occurrence of Nangqên earthquake. So, we propose that the Nangqên earthquake could be an independent event.
|Number of pages||15|
|Journal||Chinese Journal of Geophysics|
|Publication status||Published - 1 Sep 2012|
- Coulomb failure stress
- Earthquake stress triggering
- Nangqên earthquake
- Yushu earthquake