Interaction mechanism of strong earthquakes in the tectonic transition zone:a numerical study of four Ms＞6.0 Yutian earthquakes from 2008 to 2020
Following the 2008 Yutian MS7.3 earthquake,strong earthquakes such as Ms6.2 in 2012,Ms7.3 in 2014,and Ms6.4 in 2020 occurred successively in the tectonic transition zone that located at the southwestern segment of the Altyn Tagh fault zone.Seismic interaction provides the key to understanding the mechanism of earthquakes.In this study,we construct a three-dimensional viscoelastic finite element model of the southwestern segment of the Altyn Tagh fault and its adjacent region,to analyze the interaction between four strong earthquakes,and further calculate the co-and combined(co-plus post-seismic)Coulomb stress change of the faults caused by these strong earthquakes,with the co-seismic slip model as constraints.The results show that the combined Coulomb stress change before the occurrence of the subsequent three earthquakes are-1.89×104 Pa,3.63 × 104 Pa,and 1.04 × 104 Pa,respectively,indicating that the 2008 Yutian earthquake delayed the occurrence of the 2012 Yutian earthquake,while the 2008 and 2012 Yutian earthquakes jointly triggered the 2014 Yutian earthquake,and also the three earthquakes advanced the 2020 Yutian earthquake.Meanwhile,stress transfer between strong earthquakes at different tectonic locations shows that earthquakes in the extensional area at the end of the southwestern segment of the Altyn Tagh fault cast a positive effect to the event on the NE-trending sinistral strike-slip fault,which advances the occurrence of it.On the contrary,it also delays the occurrence of strong earthquakes on the nearly NS-trending normal fault in the extensional area of the southwestern segment end of the Altyn Tagh fault.Comprehensive analysis shows that the Altyn Tagh fault and the west segment of the Gozha Co fault experience a significant stress increase(＞1.0×105 Pa),and more attention should be paid to the seismic hazard.
Yutian earthquakeCo-seismic slip distributionFinite element modelCoulomb stress changeSeismic hazard
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