川滇菱形块体东边界库仑应力演化及强震发生概率估算

本研究基于分层黏弹介质模型，考虑强震或大地震同震位错、震后黏滞松弛及主断层段震间构造应力加载三方面效应，给出1480年以来，川滇菱形块体东边界鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带共20个断层段由三方面效应引起的累积库仑应力变化随时间的演化，分析强震间相互作用和强震发生的应力累积背景，定性分析各断层段的地震危险性.同时，分别采用现今台网地震目录和川滇菱形块体东边界各断层段强震复发间隔两种资料，定量计算2030年各断层段的强震发生概率；并基于摩擦本构理论，将周边强震引起的库仑应力变化量作为应力扰动，修正强震发生概率的计算结果.各断层段累积库仑应力演化的结果表明，鲜水河断裂带中部八美段、色拉哈段及南部磨西段、安宁河断裂带冕宁-西昌段、小江断裂带北部巧家-东川段和南部建水段的累积库仑应力显著增加.修正的强震发生概率计算结果显示，鲜水河断裂带中部八美-色拉哈-康定一带、安宁河断裂带冕宁-西昌段、小江断裂带南部华宁-建水一带强震发生概率较高，地震危险性值得关注.本研究基于库仑应力演化计算定性分析强震危险性的同时，基于摩擦本构律理论，结合地震引起的应力扰动和强震发生背景，定量计算修正的强震发生概率，为川滇菱形块体东边界强震危险地点及中长期发震紧迫程度判定提供方法和依据.

Coulomb stress evolution and future earthquake probability along the eastern boundary of the Sichuan-Yunnan block

Using a more realistic model of multi-layered viscoelastic media, the interseismic Coulomb accumulation related to tectonic loading and the Coulomb stress changes caused by coseismic dislocation and postseismic viscoelastic relaxation of the previous earthquakes were calculated. We analyzed the relationship between strong earthquakes and the stress accumulation background before every earthquake, studied the Coulomb stress evolution caused by the three effects for the 20 main segments of the Xianshuihe fault zone, the Anninghe fault zone, the Zemuhe fault zone, and the Xiaojiang fault zone, since 1480. Based on these results, we qualitatively analyzed the possible locations of future strong earthquaskes.
The background seismicity of strong earthquake was estimated using two kinds of data, one is the micro- and moderate earthquake catalog of the present seismic networks, and another is the strong earthquake recurrence data. Based on the friction constitutive law developed by Dieterich (1994), combined with the background seismic activity and the Coulomb stress disturbance caused by the nearby strong earthquakes, the corrected future earthquake probability for different fault segments were quantitatively calculated.
The results of the cumulative Coulomb stress evolution for different segments show that, the Coulomb stress increases significantly in Bamei segment, Selaha segment, and Moxi segment of the Xianshuihe fault zone, Mianning-Xichang segment of the Anninghe fault zone, Qiaojia-Dongchuan segment and Jianshui segment of the Xiaojiang fault zone. The results of the corrected future earthquake probability show that, the areas nearby Baimei, Yalahe, and Kangding in the central part of the Xianshuihe fault zone, Mianning-Xichang segment of the Anninghe fault zone, and the area nearby Huaning-Jianshui in the southern part of the Xiaojiang fault zone, have high probability of strong earthquake and seismic hazard.