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多分量钻孔应变仪可直接测量钻孔内不同方位的直径变化。为了将测量结果转换成应变,需要一个标定矩阵,该标定矩阵通过分析已安装的应变仪对已知应变的反应估算得到。应变固体潮的理论值往往作为已知应变。本文对板块边界观测台网中12个钻孔应变仪进行上述分析,假定每个应变仪的4个元件反应应变张量的3个水平分量以及垂直分量。方位修正通过估算得到。每个PBO应变仪的第四个元件提供的信息能够用来降低耦合系数出错的可能性。加利福尼亚的3个PBO钻孔应变仪的潮汐观测值和理论值非常吻合,其他仪器的观测值也曾证实过该地区的潮汐理论值;另外,安装在Oregon和华盛顿的6台钻孔应变仪的潮汐观测值和理论值也吻合,但在那里未曾有其他仪器记录过应变固体潮。出乎意料的是,好几台应变仪有很大的垂直应变耦合系数,这增加了仪器对大气压力的响应。垂向耦合减弱面应变甚至改变其符号,面应变是由固体潮或地球深部活动引起,垂直应变和面应变的符号相反。但是垂向耦合不会消弱剪应变的响应。PBO钻孔应变仪可以提供标定后的剪应变时间序列,反应与构造活动或岩浆过程相关的应变变化。
Multi-component borehole strain gauge can directly measure the diameter changes in different directions within the borehole. In order to convert the measurement result to a strain, a calibration matrix is needed, which is estimated by analyzing the response of the installed strain gauge to a known strain. The theoretical value of strained solid tide tends to be known as strain. This analysis of the 12 borehole strain gauges in the Plate Boundary Observatory network assumes that the four elements of each strain gauge respond to the three horizontal and vertical components of the strain tensor. Azimuth correction obtained by estimation. The information provided by the fourth element of each PBO strain gauge can be used to reduce the possibility of errors in the coupling coefficients. The tidal observations of the three PBO borehole strain gauges in California are in good agreement with the theoretical values, and the observations from other instruments have also demonstrated the tidal theoretical values in the area; in addition, the six borehole strain gauges installed in Oregon and Washington Tidal observations also agree well with theoretical values, but no other device has recorded a tidal solid strain. Unexpectedly, several strain gauges have a large vertical strain-coupled coefficient, which increases the instrument’s response to atmospheric pressure. Vertical coupling weakens the surface strain or even changes its sign. Surface strain is caused by solid tide or deep earth activity, with opposite signs of vertical strain and surface strain. But the vertical coupling will not weaken the shear strain response. PBO borehole strain gauges provide a calibrated series of shear strain times that reflect strain changes associated with tectonic activity or magmatism.