周期气压波对地壳岩石应变测量影响的理论解

Theoretical solution of periodic pressure wave effect on crustal rock strain measurement

钻孔应变仪用于测量地壳岩石应变,分为体应变仪和分量式应变仪两类,前者进行体应变观测,后者功能之一是测量面应变.大量观测事实表明气压对二者的影响很显著,且具有连续性.因此,建立相应力学模型,求解气压影响系数,探寻变化规律很有必要,对地震前兆观测背景场的正确分析有实际意义.根据Fung给出的气压波动应力解,定义了长、短周期气压波的概念和分界点,又结合已有的钻孔应变观测模型,分别推导出体应变与面应变对周期气压波的弹性响应方程,并给出气压影响系数理论解,分析了二者之间的关系和差异,并将体应变理论气压影响系数与京、津、冀、鲁等地区部分台站的实测值进行了比较,结果显示两组曲线基本相符,模型的正确性和可靠性初步得到验证.

Borehole strainmeter is used to measure crustal rock strain,which can be divided into two types:volumetric strainmeter and component strainmeter.The former is used for Volumetric strain observation,and one of the latter functions is to measure area strain.A large number of observations show that the effect of air pressure on the two is significant and continuous.Therefore,it is necessary to establish the corresponding mechanical model,to solve the pressure influence coefficient and to explore the law of change.It is of practical significance to the correct analysis of the background field of earthquake precursor observation.Therefore,it is necessary to establish the corresponding mechanical model,to solve the pressure influence coefficient and to explore the law of change.It is of practical significance to the correct analysis of the background field of earthquake precursor observation.According to the stress wave stress solution given by Fung,the concept and demarcation point of long and short periodic pressure wave are defined,and the elastic response equation of the volumetric strain and area strain to the periodic pressure wave are derived by combining the existing borehole strain observation model,the theoretical solution of the influence coefficient of air pressure is given,and the relationship and difference between the two are analyzed,and the pressure coefficient of the volumetric strain theory is compared with the measured values of some stations in Beijing,Tianjin,Hebei,Shandong and other regions.The results show that the two sets of curves are basically consistent,and the correctness and reliability of the model are preliminarily verified.