2023年12月18日甘肃积石山M 6.2地震的前兆异常和孕震过程  

Precursory anomalies and seismogenic process of the 2023 Jishishan,Gansu,M 6.2 earthquake

作　　者：许健生[1] 李丽[1] 张瑜 闫万生 杨晓鹏 武银 陈双贵 陈雪梅 XU Jiansheng;LI Li;ZHANG Yu;YAN Wangsheng;YANG Xiaopeng;WU Yin;CHEN Shuanggui;CHEN Xuemei(Institute of Geophysics,CEA,Beijing 100081,China;Gansu Earthquake Agency,Lanzhou 730000,Gansu,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]甘肃省地震局,甘肃兰州730000

出　　处：《地震工程学报》2024年第4期857-866,共10页China Earthquake Engineering Journal

基　　金：国家重大科学仪器设备开发专项(2016YFF0103400);中国地震局2024年老科技工作者科研专项。

摘　　要：为了寻找确切的地震前兆异常,在2023年12月18日甘肃积石山M 6.2地震后,对甘肃省临夏地震台观测资料进行分析,发现临夏台所处地块从2023年1月10日起就处在构造应力的作用下,地块内裂隙张开,吸纳空气,导致钻孔与地面气压差ΔP负异常;从2月22日起,自然电位差ΔV和单极电阻率ρK相继出现异常变化;从3月16日起,开始了小幅度的预滑活动Xpo,并于8月11日前后达到峰值Xpm。预滑活动使临夏台所处地块内多个小裂隙快速张开,并吸纳气体,导致钻孔气压在12月6日起出现多个负气压脉冲G P,这些异常现象直到震后才结束。震前十几个小时的临震预滑活动使得积聚在孕震断层上的应力进一步加大,克服了断层面上的摩擦力,导致孕震断层失稳破裂,发生了积石山M 6.2地震。鉴于观测到的预滑活动和前兆异常发生的时间、空间都与积石山M 6.2地震有较好的相关性,推测临夏台震前观测到的地块预滑活动、气压差变化、气压脉冲、自然电位差和单极电阻率变化可能是M 6.2地震的前兆异常。前兆异常时空演化过程表明,积石山M 6.2地震的孕震过程分4个阶段。因此,关注震前地块预滑活动和各类前兆异常,对预测未来破坏性地震和研究孕震过程有一定的前兆意义。We aimed to study the precursor anomalies of the M 6.2 earthquake in Jishishan County,Gansu Province,on December 18,2023.For this purpose,this study analyzed data recorded at the Linxia seismic station in Gansu Province.The outcomes of the analysis revealed that since January 10,2023,the fissures caused by this earthquake in the block in which the Linxia station is located have already opened up.It was observed that these fissures absorb gases rapidly under the action of tectonic stress,resulting in a negative anomaly of air pressure(ΔP)between the borehole and the ground.Since February 22,there have been several cases of abnormal changes in the natural potential differenceΔV and unipolar resistivityρK.The small-scale preslip activity Xpo began on March 16,and it attained the peak Xpm around August 11.The preslip activity caused numerous small cracks in the Linxia block to open and absorb gas quickly,resulting in a large number of negative pressure pulses G p in the borehole from December 6.These anomalies ended after the earthquake.After lasting for more than 10 h,the preslip activity increased the stress accumulated on the seismogenic fault before the earthquake.The fault became unstable and ruptured when the stress exceeded the frictional force on the fault plan,which may have led to the occurrence of the M 6.2 earthquake.It is speculated that preslip activity and variations in pressure difference,pressure pulse,natural potential difference,and unipolar resistivity,which were observed at the Linxia station before the Jishishan M 6.2 earthquake,may be precursors of these anomalies.This conclusion was drawn in consideration of the fact that there was a good correlation between the anomalies and the earthquake.The temporal and spatial evolution of the precursory anomalies showed that the seismogenic process of the Jishishan M 6.2 earthquake can be broadly categorized into four stages.Therefore,it is highly important to pay close attention to preslip activity and various precursory anomalies before an earthquak

关 键 词：预滑活动 气压差ΔP 气压脉冲G P 地震前兆异常 孕震过程 甘肃积石山M 6.2地震 

分 类 号：P315[天文地球—地震学]