1900年以来巴颜喀拉块体应力演化与周缘强震关系的数值模拟研究

以巴颜喀拉块体为研究对象，考虑区域地质构造差异，主要活动断裂带，活动块体和边界断裂带的划分结果，引入深部三维速度结构，建立能反映地表起伏和岩石圈分层结构的青藏高原地区三维黏弹性有限元模型.以地壳水平运动速率观测值和最大主压应力方向测量值为约束条件重建研究区现今构造背景应力场.在此基础上模拟了自1900年以来巴颜喀拉块体周缘的7级以上强震序列，从库仑破裂应力角度研究了应力演化与强震的关系、强震之间的相互作用关系以及长期构造加载对强震的影响.研究结果表明，巴颜喀拉块体周缘强震的发生可能与震源区总应力的增加有关.2008年汶川地震导致龙门山断裂带南段应力增加，表明汶川地震对2013年芦山地震有促进作用.鲜水河断裂带上的7级以上强震序列对发生在邻近龙门山断裂带上的2008年汶川地震和2013年芦山地震有延迟作用.

Numerical simulation of relationship between stress evolution and strong earthquakes around the Bayan Har block since 1900

Taking the Bayan Har block as the research object, a 3-D viscoelastic finite element model of the Tibetan plateau, including the Bayan Har block, is constructed, which considers differences in the regional geologic structure, the major active fault zone, active blocks, deep 3D velocity structure, surface topographic relief and layered lithosphere. Using this model, the present tectonic background stress field in the research area is reconstructed by using the constraints of measured crustal horizontal movement rates and the direction of the maximum principal compressive stress. Then the historical strong earthquake sequences of M ≥ 7 around the Bayan Har block since 1900 AD are simulated. From the perspective of Coulomb failure stress, the relationship between stress evolution and strong earthquakes, the interaction between strong earthquakes, and the influence of long-term tectonic loading on strong earthquakes are examined. The results show that the occurrence of strong earthquakes around the Bayan Har block may be related to the increase of the total stress in the source area. The 2008 Wenchuan earthquake resulted in an increase of the stress in the southern section of the Longmenshan fault zone, indicating that this event promoted the 2013 Lushan earthquake to the southwest. The strong earthquakes with M ≥ 7 on the Xianshuihe fault zone have a delaying effect on the 2008 Wenchuan earthquake and the 2013 Lushan earthquake in the adjacent Longmenshan fault zone.