Visco-elastic stress triggering model of Tangshan earthquake sequence |
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| Authors: | Yong-ge Wan Zheng-kang Shen Yue-hua Zeng Shu-zhong Sheng and Xiao-feng Xu |
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| Institution: | (1) Institute of Disaster Prevention Science and Technology, Sanhe, 065201, China;(2) Institute of Geophysics, China Earthquake Administration, Beijing, 100081, China;(3) Department of Geophysics, Peking University, Beijing, 100871, China;(4) U. S. Geology Survey, Golden, CO 80401, USA |
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| Abstract: | We calculated the Coulomb failure stress change generated by the 1976 Tangshan earthquake that is projected onto the fault
planes and slip directions of large subsequent aftershocks. Results of previous studies on the seismic failure distribution,
crustal velocity and viscosity structures of the Tangshan earthquake are used as model constraints. Effects of the local pore
fluid pressure and impact of soft medium near the fault are also considered. Our result shows that the subsequent Luanxian
and Ninghe earthquakes occurred in the regions with a positive Coulomb failure stress produced by the Tangshan earthquake.
To study the triggering effect of the Tangshan, Luanxian, and Ninghe earthquakes on the follow-up small earthquakes, we first
evaluate the possible focal mechanisms of small earthquakes according to the regional stress field and co-seismic slip distributions
derived from previous studies, assuming the amplitude of regional tectonic stress as 10 MPa. By projecting the stress changes
generated by the above three earthquakes onto the possible fault planes and slip directions of small earthquakes, we find
that the “butterfly” distribution pattern of increased Coulomb failure stress is consistent with the spatial distribution
of follow-up earthquakes, and 95% of the aftershocks occurred in regions where Coulomb failure stresses increase, indicating
that the former large earthquakes modulated occurrences of follow-up earthquakes in the Tangshan earthquake sequence. This
result has some significance in rapid assessment of aftershock hazard after a large earthquake. If detailed failure distribution,
seismogenic fault in the focal area and their slip features can be rapidly determined after a large earthquake, our algorithm
can be used to predict the locations of large aftershocks.
Foundation item: National Natural Science Foundation of China (40374012 and 40874022). |
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| Keywords: | Tangshan earthquake stress triggering viscoelasticity stress direction |
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