【摘要】 基于青藏高原及邻区的三维粘弹性有限元模型,讨论2008年于田MS7.3级地震与2014年于田MS7.3级地震之间的关系,并研究2014年于田MS7.3级地震的发生造成周围断层的库仑破裂应力变化。初步结果表明:1)2008年于田MS7.3级地震在2014年于田MS7.3级地震震中滑动方向上产生的库仑破裂应力变化高于地震触发的阈值0.01 MPa,存在明显的触发作用。在视摩擦系数分别取0.4和0.6时,震源区同震库仑破裂应力变化为0.0167 MPa和0.0170 MPa;而考虑粘弹性松弛作用时产生的库仑应力增加量分别为0.0187 MPa和0.0194 MPa。结合断裂带构造应力年累计速率的结果,2008年于田地震的发生造成2014年于田地震提前21.4~24.9 a;2)在较短的时间尺度内,对于距离相近的两次地震之间,同震产生的应力变化远大于粘弹性松弛效应产生的变化;3)2014年于田MS7.3级地震的发生造成阿尔金断裂中北段、玛尼—玉树断裂中段、东昆仑断裂西段、柴达木北缘断裂东段、西秦岭北缘断裂西段等不同程度的加载效应,地震危险性有所增强。其中阿尔金断裂中段库仑应力增加最为明显,最大达2.8×10–3 MPa;玛尼—玉树断裂中段次之,应力增加量最大达5.6×10–4 MPa;东昆仑断裂西段应力增加量最大达4.75×10–4 MPa。而玛尼—玉树断裂西段库仑破裂应力最大卸载量达3.6×10–3 MPa。更多还原

【Abstract】 In this paper, the three-dimensional finite element model for the Tibetan Plateau and its adjacent region was employed to explore the possible relationship between the 2014 Yutian MS7.3 earthquake and the antecedent Yutian MS7.3 earthquake in 2008. Then, the coseismic Coulomb failure stress change of the surrounding faults caused by the Yutian MS 7.3 earthquake in 2014 was analyzed. Some preliminary conclusions have been reached: 1) the Coulomb failure stress change caused by the Yutian MS7.3 earthquake in 2008, which was projected in the slip direction of the 2014 Yutian earthquake epicenter, exceeded the earthquake triggering threshold, which demonstrates the apparent triggering effect. Specifically, the coseismic Coulomb failure stress changes were 0.0167 MPa and 0.0170 MPa when we assumed 0.4 and 0.6 as the apparent friction coefficients; meanwhile, the Coulomb failure stress changes incorporating the coseismic and viscoelastic relaxation effects were 0.0187 MPa and 0.0194 MPa respectively. The later 2014 Yutian earthquake advanced the antecedent Yutian earthquake in 2008 by 21.4~25.9 a, as shown by the tectonic stressing rate; 2) in a relatively short time scale, the stress change induced by the coseismic effect is greater than the viscoelastic effect for the two successive earthquakes; 3) the Coulomb failure stresses increased along the mid-north segment of Altun fault, middle segment of Mani-Yushu fault, western segment of Eastern Kulun fault, eastern segment of northern Qaidam fault and western segment of northern margin of West Qinling, suggesting the increasing seismic risk. Among these structures, the Coulomb failure stress increased by 2.8×10-3 MPa in the middle segment of Altun fault at the maximum, 5.6×10-4 MPa in the middle segment of Mani-Yushu fault, and 4.75×10-4 MPa in the western segment of Eastern Kunlun fault. In addition, the Coulomb failure stress decreased by 3.6×10-3 MPa in the western segment of Mani-Yushu fault.更多还原