Numerical Simulation Of Strong Earthquake Activity On The Margin Of Bayanhar Block And Longmenshan Area

The Bayanhar block and Longmenshan area as the research object, considering the difference of regional geological structure, the main active fault zone, additional surface gravity, the 3-D viscoelastic finite element model of Qinghai-Tibet plateau including Bayanhar block and Longmenshan area are established respectively. Using the observed values of crustal horizontal movement as constraint condition, the present tectonic background stress field in the research area is reconstructed. Based on it, the 14 strong earthquakes (Ms≥ 7.0) occurring around Bayanhar block and 5 strong earthquakes (Ms≥ 7.0) in Longmenshan region since 1900 is simulated, respectively. From the viewpoint of coseismic Coulomb failure stress and equivalent stress, the relationship between strong earthquakes in the models of different scales is investigated.The research results indicate that:From the viewpoint of coseismic Coulomb failure stress, in Bayanhar block area, it has 7 earthquakes advance its following earthquakes, but the coseismic Coulomb failure stress value does not exceed the threshold value to trigger the following earthquake. In Longmenshan area, it has 3 earthquakes accelerate the following earthquakes, in which the Wenchuan earthquake triggers the Lushan earthquake. Considering the intersersmic effec furtherly, the 3 earthquakes in Longmenshan possibly trigger its following earthquakes. From the viewpoint of coseismic equivalent stress, in Bayanhar block and Longmenshan area, there are 8 and 4 earthquakes advance the following earthquakes, respectively. Among the 11 earthquakes occurring on the margin of Bayanhar block before the Wenchuan earthquake, there are 8 earthquakes accelerate the Wenchuan earthquake.The research results also show that:the most aftershocks of Wenchuan earthquake and Lushan earthquake are triggered by their main shock, and only 6.03% aftershock of Lushan earthquake is triggered by Wenchuan earthquake. The coseismic Coulomb failure stress of the location of Lushan earthquake caused by Wenchuan earthquake is about 0.016MPa. If calculation according to the cumulative rate of the year of Coulomb stress in the southern segment of the Longmenshan fault zone 0.4-0.6×10-3MPa.a-1, the Wenchuan earthquake advances the Lushan earthquake nearly 27～40 years. In addition, the Wenchuan earthquake and Lushan earthquake cause the Coulomb stress increase in the southern segment of the Xianshuihe fault zone and Huya fault, which raise the possibility of earthquake in this area in the future.