2023年甘肃积石山M_(S)6.2地震对周围断层的应力影响及对余震的触发作用

Stress change on surrounding faults and triggering of aftershocks by the 2023 Jishishan M_(S)6.2 earthquake in Gansu,China

2023年12月18日,甘肃省临夏州积石山县发生M_(S)6.2地震,震中位于拉脊山断裂带。为深度剖析本次地震对周围断层和后续地震的静态库仑破裂应力影响,文章基于地震破裂模型参数和弹性半空间模型,计算积石山M_(S)6.2地震在周围主要断层上不同深度产生的静态库仑破裂应力变化,并评估这些应力变化对未来地震危险性的影响。结果显示:本次地震使青海南山—循化南山断裂、拉脊山北缘断裂和拉脊山南缘断裂部分区域的库仑破裂应力显著增加,青海南山—循化南山断裂东段的库仑破裂应力增加远超出静态应力触发阈值,并达到了0.022 MPa,表现出较高地震危险性;其他断层也呈现出不同程度的库仑应力变化,拉脊山北缘断裂和拉脊山南缘断裂部分区域的应力卸载量达到了万帕,青海南山—循化南山断裂除东段外的其他分段和庄浪河断裂的应力卸载量达到了百帕。对不同震源深度下断层库仑破裂应力变化进行对比分析,发现深度变化对此次地震库仑破裂应力变化模式影响很大。文章还计算了本次地震在较大余震断层面上的库仑破裂应力,结果表明:甘肃积石山M_(S)6.2地震在后续三次M_(S)≥4地震的断层面上产生的库仑破裂应力分别为0.024 MPa、0.033 MPa和0.034 MPa,均超过触发阈值(0.01 MPa),表明M_(S)6.2地震对这三次地震具有明显的触发作用。文章可为该地区未来地震可能性与危险性的评估提供一定的参考。

On December 18,2023,an M_(S)6.2 earthquake occurred in Jishishan County,Linxia Prefecture,Gansu Province,China.The earthquake is located on the Lajishan fault.A comprehensive analysis of the impact of this earthquake on the static Coulomb failure stress(CFS)of surrounding faults and aftershocks was performed.The changes in static CFS at different depths along the surrounding faults due to the Jishishan M_(S)6.2 earthquake were calculated based on the parameters of earthquake rupture and elastic half-space models,and the future potential seismic hazard in the study region was then estimated based on the CFS changes.Results indicate that the event substantially increased the CFS in some areas of the Qinghai Nanshan-Xunhua Nanshan fault and the northern and southern margin faults of Lajishan.Particularly,the eastern segment of the Qinghai Nanshan-Xunhua Nanshan fault experienced a CFS increase far exceeding the static stress triggering threshold,reaching 0.022 MPa,indicating a potentially high seismic hazard.Other faults also displayed various degrees of CFS changes,with stress unloading amounts reaching 10000 Pa in some areas of the northern and southern margin faults of Lajishan and 100 Pa on the Zhuanglanghe fault and other segments of the Qinghai Nanshan-Xunhua Nanshan fault,with the exception of the eastern segment.Furthermore,a comparative analysis of CFS changes on faults at different depths revealed the considerable influence of depth variation on the CFS pattern of the earthquake.However,the increase in CFS along the Qinghai Nanshan-Xunhua Nanshan fault is crucial.This study provides a reference for evaluating the possibility and risk of future earthquakes in the study region.Moreover,the CFS changes due to the mainshock on the fault planes of some large aftershocks were calculated.The CFS on the fault planes of three subsequent M_(S)≥4 earthquakes were estimated as 0.024,0.033,and 0.034 MPa,and all exceeded the triggering threshold,displaying the triggering effect of the M_(S)6.2 earthquake on the three events.