钻孔应变仪观测的面应变潮汐因子初步分析

Analysis on strain tidal factor observed borehole strainmeters

钻孔应变仪直接观测的是筒壁的直径变化,并不是地壳应变.在进行潮汐分析时必须首先将观测值转换为应变值.基于2008年1月1日至2013年4月19日全国部分钻孔应变观测资料,选取应变差分值进行计算.我们首先对观测数据进行相对标定、绝对标定,反演得到地理坐标系下观测点的应变分量.采用球状径向不均匀弹性地球模型计算理论应变固体潮.最终运用调和分析方法,得到面应变固体潮的M2波潮汐振幅因子.分析潮汐因子变化特征以及影响潮汐因子动态变化的因素,发现观测点的纬度和高程对潮汐因子的影响可以忽略,而围岩的性质对潮汐因子影响明显.

The borehole strainmeters measure changes in diameter of the cylindrical strainmeter housing at different azimuths.Because the strainmeter and the grout in which it is emplaced have different elastic moduli,so the strain is not the same as that which the formation would have experienced were the strainmeter not there.Therefore,during the tide analysis,observations will be converted to strain values.Using the data observed borehole strainmeters from January 1,2008 to April19,2013,relative calibration and absolute calibration,the final,we know the observation points strain components in geographical coordinates. At the same time, we calculate theoretical tidal strain using the radially heterogeneous spherical elastic earth model.We estimate the amplitudes of the M2 in the strainmeter output and the theoretical tidal strain using the t_tide package.We focus the areal strain and its change,so we use the differential value.We discuss the factors affecting tidal factor.We realize the latitude and elevation don＇t affect tidal factor, but the characteristic of the rock significantly affect tidal factor.