北祁连山东段强震间静态库仑应力变化与触发作用研究
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中国地震局地震预测研究所基本科研业务专项(2013A77;2013-2)


Static Coulomb Stress Changes and Triggering Interaction amongStrong Earthquakes in the Eastern Segment of North Qilian Mountain
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    摘要:

    基于Coulomb3.3软件,通过研究地震累加与单震的库仑应力变化对后续地震的触发关系,对北祁连山东段及邻区自1561年以来的9次强震静态库仑应力变化进行了研究。结果表明:对于叠加现象来说,后一地震事件除了门源地震落在应力影区外,先前地震活动对后续地震都产生了明显的触发作用,库仑应力变化在0.1~4.066 bar之间;而对于单独事件的应力变化,断层距较小的地震之间相互触发的影响较大。根据库仑应力变化和年应力累积量的比值,得出地震在没有先前地震作用下还需要的应力累积时间。最后根据大震后区域断裂库伦应力变化及断裂强震活动历史等特征,对本区未来强震地震危险性进行分析,得出本区未来地震危险区位于云雾山断裂以及天祝-景泰—古浪一带的金强河断裂上。

    Abstract:

    Earthquakes are a natural phenomenon caused by sudden rupture and slippage of crustal rocks after stress reaches the point of rock failure.The coseismic dislocations of a major earthquake not only cause the stress state changes in adjacent areas, but also change the Coulomb stress.Research shows that a very small static Coulomb stress changes can trigger seismic activity (i.e.,earthquakes).Therefore,it is important to explore the relationship between Coulomb stress changes and earthquake triggering.First of all,we conducted primary research for strong earthquakes by Coulomb 3.3 on the static Coulomb stress changes with the primary study region being the eastern margin of north Qilian Mountain and adjacent area from 1561 to present. Meanwhile,we used cumulative and individual methods to calculate the Coulomb stress changes between foreshocks and aftershocks.Our results show that the next events,except Menyuan earthquake in 1986,would occur in the stress triggering area.The value of changes is between 0.1 bar and 4.066 bar,and trigger rate reached a high of 87.5%.In other instances,when the source fault is closed to receive fault,the former event can trigger the next.Secondly,according to the relationship between Coulomb stress changes and stress accumulation rate,we calculated the stress accumulated before the next event,not considering foreshocks.Finally,we assessed the future strong seismic hazard for this area according to earthquake migration and stress triggering.We used Okada’s method to calculate the change of static Coulomb failure stress among faults for the study area.In 1920 and 1927,two magnitude 8 earthquakes occurred,prior to the earthquakes the Coulomb stress significantly increased in the eastern side of Yunwu Mountain and western part of Jingtai-Tianzhu-Gulang.This suggests that an increase of Coulomb stress may forecast a triggered earthquake.It is noteworthy that the Tianzhu 6.2 earthquake occurred in the western part of the danger zone after two prior earthquakes.Considering the Coulomb stress triggering and the history of seismic activity,future earthquake risk should be strong in this area as well as the eastern side of Yunwu Mountain and Jinqianghe fault zone in the western part of Jingtai-Tianzhu-Gulang.This paper attempts to combine Coulomb stress adjustment and fracture characteristics with seismic activity.Results are consistent with other approaches in the Northeastern Qilian area,indicating that Coulomb stress changes can be used as an indicator of oncoming seismic activity. Application of this method will require further improvement to assess future seismic risk.

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刘方斌,王爱国,袁道阳.北祁连山东段强震间静态库仑应力变化与触发作用研究[J].地震工程学报,2014,36(2):360-371,379. LIU Fang-bin, WANG Ai-guo, YUAN Dao-yang. Static Coulomb Stress Changes and Triggering Interaction amongStrong Earthquakes in the Eastern Segment of North Qilian Mountain[J]. China Earthquake Engineering Journal,2014,36(2):360-371,379.

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  • 在线发布日期: 2014-08-04