钻孔应变资料的可靠性分析

RELIABILITY ANALYSIS OF BOREHOLE STRAINMETRY OBSERVATIONS

在钻孔应变观测中,仅用实际观测资料与理论固体潮进行对比还不能完全反映观测数据的一致性和可靠性,也无法准确确定其趋势性变化是否是应变变化,而地震前兆研究需要明确这种趋势性变化的性质。从弹性力学理论中导出并通过实测资料验证:同一钻孔中相差45°分布的四分量应变1号与3号测值之和理论上应等于2号与4号测值之和,同时还应等于1.3倍体应变测值;用四分量应变观测资料计算出η值,其绝对值越接近零资料的可靠性越好,这种方法有可能为钻孔应变观测资料的质量评价提供一种新的参考依据;有两种以上钻孔应变手段的台站可开展对比观测,只有四分量钻孔应变一种观测手段的台站要开展1号+3号与2号+4号资料的自检分析,以获取更加可靠的观测资料。

Reliability should be the key in precursor observation. Usually, we just compare the measurements and variation with the theoretic earth tide to judge whether the data are reliable. However, the way can＇ t determine the consistency of data and the long-term trend should be affirmed firstly in precursor analysis. According to the elastic mechanics theory and the observation in-situ, it is shown that for a 4 components strain instrument, their component directions spread with 45 degree angle, the sums of measure values of unit 1 （1#） and 3（3#） should be the same with that of unit 2（2#） and 4（4#）, and the sum value is also equal to 1.3 times of the volume strain. We can calculate a value 7/by use of the 4 components strain measurements, its absolute value is the more close to 0, the more reliability of the observation. This way may provide a new evidence in estimation of observation reliability. In order to get more reliable observation, contrasting analysis can be held in those observatory with two type of strain instruments. Otherwise for those observatory with just a component strain instrument, self test , that 1# ＋ 3# should be equal to 2# ＋ 4#, may also be used to verify the reliability.