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A Review of the Calculation Formula for the Fourcomponent Borehole Strainmeter and Application to Earthquake Cases 
SU Kaizhi

Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China


摘要: 
Based on the principle formula for the fourcomponent strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal strains calculated afterwards are the indirect result. The problems of practicality of the sensitivity coefficients A and B of plane strain and shear strain are then discussed. Based on this idea, we analyzed the observation data of several fourcomponent borehole strainmeters near the epicenter of the Yiliang M_{S}5.7 earthquake in 2012 and the Ludian M_{S}6.5 earthquake in 2014 in the Zhaotong area, Yunnan Province. The results show that the analysis based on the perspective of plane strain and shear strain has an obviously better effect than that based on the component readings, and can directly peel off the respective abnormality of the plane strain and shear strain. In addition, the correlation coefficient curves between measured data of two plane strains show significant anomalies which often occur several days before and during the earthquake. 
关键词: Fourcomponent borehole strainmeter Ludian M_{S}6.5 earthquake Yiliang M_{S}5.7 earthquake Plane strain abnormality Shear strain abnormality Selftest of data Strain anomaly 
DOI：10.19743/j.cnki.08914176.201901008 
分类号: 
基金项目:The project is sponsored by the Central Level Scientific Research Institutes of Basic R&D Special Fund Business of the Institute of Crustal Dynamics,CEA (ZDJ201725). 

A Review of the Calculation Formula for the Fourcomponent Borehole Strainmeter and Application to Earthquake Cases 
SU Kaizhi

Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China

Abstract: 
Based on the principle formula for the fourcomponent strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal strains calculated afterwards are the indirect result. The problems of practicality of the sensitivity coefficients A and B of plane strain and shear strain are then discussed. Based on this idea, we analyzed the observation data of several fourcomponent borehole strainmeters near the epicenter of the Yiliang M_{S}5.7 earthquake in 2012 and the Ludian M_{S}6.5 earthquake in 2014 in the Zhaotong area, Yunnan Province. The results show that the analysis based on the perspective of plane strain and shear strain has an obviously better effect than that based on the component readings, and can directly peel off the respective abnormality of the plane strain and shear strain. In addition, the correlation coefficient curves between measured data of two plane strains show significant anomalies which often occur several days before and during the earthquake. 
Key words: Fourcomponent borehole strainmeter Ludian M_{S}6.5 earthquake Yiliang M_{S}5.7 earthquake Plane strain abnormality Shear strain abnormality Selftest of data Strain anomaly 
