汶川大震时福建四种观测系统的体应变响应分析

Analysis of Volumetric Strain Response Caused by Wenchuan Earthquake Based on Observation Data of Well Level Observation Systems

采用福建省有关观测点的井水位、地震仪、体应变仪与伸缩仪的分钟值观测资料对福建地区对2008年5月12日四川汶川8.0级大震的体应变响应进行了计算,计算结果表明,由井水位、体应变仪与伸缩仪所得到的对汶川大震的体应变响应的振幅为10^(-7)～10^(-8),而由地震仪所得到的体应变响应要比前者大1个数量级;并对此差异进行了分析。

On the basis of the concept that well water observation system is a natural body strain gauge, the calibration method of scale values of well water level observation were given and well level observation were converted into volumetric strains in this paper. Further, the maximum amplitudes and periods of radial and vertical displacements caused by Rayleigh surface waves of Wenchuan earthquake can be measured by seismograph, and volumetric strain responses to surface wave of Wenchuan earthquake can also be calculated according to the displacement divergence formulation. Based on the minutely values obtained from different digital observation system of well water level, seismometer, volumetric strainmeter and extensometer installed at certain observational stations in Fujian province, various volumetric strain responses of the above four observation systems to Wenehuan Ms8.0 earthquake were computed and analyzed. The results of the four observational systems show that for the well water level, volumetric strainmeter and extensometer systems, the amplitude of volumetric strain response to Wenchuan earthquake varies from 10^-7 to 10^-8, whereas for the seismograph system the corresponding amplitude is larger by one order of magnitude. Finally, this paper gives analyses on this discrepancy of amplitude.