2008年汶川M_S8.0地震在2013年芦山M_S7.0地震和2014年康定M_S6.3地震破裂区引起的库仑破裂应力

Coulomb Stress Changes Imparted in the Rupture Zones of the Lushan Earthquake and the Kangding Earthquake by the 2008 Wenchuan M_S8.0 Earthquake

2008年5月12日四川汶川发生M_S8.0地震发生之后,先后于2013年4月20日和2014年11月22日分别在汶川M_S8.0地震震中西南约80km的芦山县和约178km的康定县发生了M_S7.0和M_S6.3地震。芦山地震位于龙门山前主边界处,康定地震位于鲜水河断裂带上。芦山地震发生前有几位作者先后计算了汶川M_S8.0地震引起的库仑破裂应力,分析了其对周围断层的影响。本文对这些研究结果进行了简要回顾,并根据芦山地震和康定地震的实际发震断层面参数,计算了汶川M_S8.0地震在芦山地震和康定地震震源深度处的水平面上以及其发震断层面上产生的库仑破裂应力,还给出了其震中处库仑破裂应力随深度的变化。结果表明,汶川M_S8.0地震发生使芦山地震震源断层面上有利于其错动发震的应力大面积增加而使康定地震震源断层面上有利于其错动发震的应力大面积减小。在芦山地震初始破裂点处引起的库仑破裂应力达0.245MPa,在康定地震初始破裂点处引起的库仑破裂应力为-0.000 63 MPa。因此,汶川M_S8.0地震的发生对芦山地震具有明显的促进作用,而对康定地震的作用不明显。在目标断层面参数已知的情况下,根据库仑破裂应力在目标断层面上的分布,可能为未来地震发生的地点提供线索,进而对地震发生的危险性进行预测。若一次地震的发生使目标断层面上有利于其错动发震的应力大面积显著增加,这种情况下库仑破裂应力对未来地震具有预测意义。

On 12 May 2008 astrong MS8.0earthquake struck Wenchuan,Sichuan province,China.After the MS8.0 Wenchuan earthquake,two earthquakes of MS7.0and MS6.3occurred on 20 April 2013and 22 November 2014respectively.Their epicenters are located in Lushan,Sichuan and Kangding,Sichuan,southwest of the epicenter of the MS8.0Wenchuan event with distances of about 80 km and 178 km.The Lushan earthquake was located at the frontier boundary of the Longmenshan mountain,and the Kangding earthquake was located on the Xainshuihe fault.Till the Lushan earthquake,several authors have calculated the Coulomb stress change imparted by the MS8.0 Wenchuan earthquake and analyzed its effect on the surrounding faults.In this paper,after a brief review of their results,the Coulomb stress changes imparted by the MS8.0 Wenchuan earthquake on the horizontal plane at the focal depth and the focal fault planes of the Lushan and the Kangding events were calculated.The Coulomb stress changes versus depth at their epicenters are obtained.The results show that the MS8.0Wenchuan earthquake have made the stress on the focal fault plane of the Lushan event increased in a large area,and that on the focal fault plane of the Kangding event decreased in a large area.The Coulomb stress change at the initial rupture point for the Lushan event is 0.245 MPa,and for the Kangding event is-0.000 63 MPa.Therefore,the MS8.0 Wenchuan earthquake would play apositive role in the occurrence of the Lushan event,but could has no significant effect on the occurrence of the Kangding event.Given parameters of the target fault plane,it could be possible that some clues for the epicenter of the future strong earthquake are provided according to the Coulomb stress changes on the horizontal plane at the focal depth and the focal fault plane,and then prediction for the future strong earthquake could be given.If a strong earthquake makes the stress on the target focal fault plane increased in a large area,the Coulomb stress change could be of important significance to the prediction of the future earthquakes.