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《Chinese Journal of Geophysics》 2016-09
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The argumentation of properties of borehole system at Linxia station,China

LIU Xu-Yan;YANG Jin-Ling;CHEN Chao-Xian;GUAN Yu-Mei;CHEN Guang;ZHAO Wen-Bo;HONG Ming-Quan;Earthquake Administration of Fujian Province;  
2 years of four-component borehole strain data and well water level data are preprocessed to remove trends and outliers at Linxia Station from 2013 to 2014.According to the literatures(Means,1982;Young and Budinas,2005),the sum of observation values of two strain measurement lines orthogonal to each other is equivalent to surface strain is equal to volume strain.Literature(Liu et al.,1988)proved that two thirds of near-ground surface strain is equal to volume strain.Therefore,the volume strain can be obtained from four-component borehole strain observation data.And the properties of the borehole system can be demonstrated from time and frequencies domain based on volume and underground well water level observation data.Results show that negative correlation between volume strain and well water level is high in time domain.The sensitivity of borehole system is—0.1620mm/10-9.Enlarged the proportion of two coordinates of volume strain and well water level observation curves of some two monthsin the two year period,we found that the peak and valley of well water level corresponds to the valley and peak of volume strain one by one,the phase lag is very small.In the frequency domain,monthly tidal factor and phase lag of diurnal and semidiurnal wave groups of volume strain and water level have been obtained with Venedikov tidal harmonic analysis method.Then the sensitivity and phase lag of the borehole strain system is calculated simply.Results show that the sensitivity of most wave groups are not only close to each other,but also close to the sensitivity of annually periodic change obtained from the time domain,while the errors of phase lag are large.Considering the phase lag obtained by arctangent is influenced by calculation error,the phase lag closed to zero which is examined from time domain should be more reliable.The analysis from time and frequency domain show that the response of well water level to volume strain is substantially linear time-invariant.The borehole system of Linxia station basically meets the superposition,homogeneity and time invariance,therefore,borehole system at Linxia station is linear time-invariant system basically.
【Fund】: 福建省地震局科研基金(SF201513)资助
【CateGory Index】: P315.7
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