易县地震台分量钻孔应变观测数据分析

Analysis of the observation data of component borehole strainmeter at Yixian Seismic Station

选取易县地震台YRY-4型分量式钻孔应变仪2012—2020年观测数据,进行Venedikov调和分析,并对2015—2020年四分量数据S_(1)、S_(2)、S_(3)、S_(4)进行自洽检验,发现应变观测数据连续性、可靠性较高。选取该台2018—2019年钻孔应变原始数据S_(1)、S_(2)、S_(3)、S_(4),利用面应变S_(1)+S_(3)、S_(2)+S_(4)相关系数,分析河北省3次ML≥4.0地震前数据异常变化,并利用剪应变S_(1)-S_(3)、S_(2)-S_(4)的大小,分析受抽水干扰的NE分量主应力方位角,判断干扰源方位,结果发现:①面应变与剪应变在地震发生前均会出现异常变化,且剪应变异常变化幅度较大,应与震中相对于观测井的位置有关;②对于受抽水干扰的钻孔应变NE分量,利用剪应变固体潮数据推算主应力方位角,可得干扰源在钻孔应变观测室NW80.96°方位,与实际位置存在一定偏差。

This study selects the observation data of YRY-4 component borehole strainmeter at Yixian Seismic Station from 2012 to 2020 to carry out a Venedikov adjustment and analysis and conduct a self-consistent test for the 2015 to 2020 YRY-4 component data S_(1),S_(2),S_(3),S_(4),and find that the continuity and reliability of strain observation data are high.The original data of S_(1),S_(2),S_(3),S_(4),of the borehole strainmeter observations from 2018 to 2019 are selected to analyze the abnormal changes before 3 ML≥4.0 earthquakes in Hebei Province by using the correlation coefficients of the face strains S_(1)+S_(3)and S_(2)+S_(4)and analyze the pumping interference influence of the NE component of the main stress by using shear strain S_(1)-S_(3)and S_(2)-S_(4)to determine the location of the interference source.The results found:①Both face strain and shear strain show abnormal changes before earthquakes and the variation amplitude of shear strain is larger.It should be related to the position of observation well relative to the epicenter;②For the NE component of the borehole strain disturbed by pumping,the interference source can be obtained in the direction of NW80.96°relative to the strain observation room using the principal stress azimuth calculated from the shear strain solid tide data.This result has a certain deviation from the actual position.