张掖M_(s)5.0级地震前高台钻孔应变异常变化研究  

The Abnormal Change of Borehole Strain at Gaotai Seismic Station Before Zhangye M_(s)5.0 Earthquake

作　　者：叶媛媛 王志栋 姜振海 YE Yuanyuan;WANG Zhidong;JIANG Zhenhai(Gansu Earthquake Agency,Lanzhou 730000,China)

机构地区：[1]甘肃省地震局,兰州730000

出　　处：《华南地震》2021年第4期56-62,共7页South China Journal of Seismology

基　　金：中国地震局监测、预报、科研三结合课题(3JH-2021049)。

摘　　要：张掖M_(s)5.0级地震前,高台分量式钻孔应变出现了显著的异常变化,排除供电、调零、气压等影响观测数据的干扰因素,研究发现该异常可能是地震前兆异常。利用离散小波分解、超限率、应变变化过程和方位角变化等分析方法提取异常,综合分析发现:NE分量和NW分量出现了破年变低值异常,NE分量较往年最低点达到-64745.46×10^(-8),超出同期2013-2018年年变均值54.38%,NW分量数据最低点达到最低值-65663.8×10^(-8),最大超出同期2013-2018年年变均值17.68%;求解(ε_(1),ε_(2),φ)后,半长轴ε2持续缓慢增大,半短轴ε_(1)加速增大张力增强,达到最大值26814.1×10^(-8),后张力加速减小至6441.6×10^(-8),震后应力逐步恢复至同期均值大小。方位角φ出现大幅偏转;替换量的差分曲线、小波分解曲线、超限率曲线在4月至8月出现明显毛刺增加现象。地震前兆异常明显,异常信息可靠。Before Zhangye M_(s)5.0 earthquake,the component borehole strain of the Gaotai station had a significant abnormal change.Excluding the interference factors such as power supply,zero adjustment and air pressure,the study found that the anomaly may be an earthquake precursor anomaly.This paper use discrete wavelet decomposition,transfinite rate,strain process and azimuth change analysis methods to extract anomalies.The comprehensive analysis shows that:the NE component and NW component have the low value anomaly of breaking annual variation.Compared with the lowest point in previous years,the NE component has reached-64745.46×10^(-8),which is 54.38% higher than the average annual variation of the same period from 2013 to 2018.The lowest point of NW component data has reached the lowest value of-65663.8×10^(-8),which is 17.68% higher than the average annual variation of the same period from 2013 to 2018.After solving(ε_(1),ε_(2),φ),the semi-major axis ε_(2) continues to increase slowly,the semi-minor axisε1 increases at an accelerated rate and the tension increases.After reaching the maximum value of 26814.1×10^(-8),the tension decreased to 6441.6×10^(-8) at an accelerated rate,and the post earthquake stress gradually recovered to the mean value of the same period.There is a large deflection of azimuth angle.The difference curve,wavelet decomposition curve and overrun rate curve of replacement quantity increased obviously from April to August.The earthquake precursory anomalies are obvious and the anomaly information is reliable.

关 键 词：钻孔应变 小波分析 超限分析 前兆异常 

分 类 号：P315.73[天文地球—地震学]