Abstract Based on theoretical analysis, we propose the concepts of apparent azimuth and apparent declination of ground tilt, and introduce the procedure of calculating the apparent declination. We use the observed data of five measurement components of the water pipe tiltmeter from 1987 to 2021 in Beijing Yanqing Xibozi and Gansu Lanzhou Shilidian stations as examples. In turn, we calculate the results for the apparent declination of the 715 measured component observations of the national ground tilt network in 2020. Results from two typical stations show that: the Xibozi station NS direction angle of apparent declination PNS=-0.1°; EW direction angle of apparent declination PEW=9.6°; NE direction angle of apparent declination PNE=12.4°; the Shilidian station NS direction angle of apparent declination PNS=0.3°; EW direction angle of apparent declination PEW=-22.5°; the maximum apparent deflection angle of 2 stations is 23.2°, the minimum value is -36.0°. From the statistical mean of the 5 components, the maximum value of the apparent deviation angle is 12.4°, the minimum value is -22.5°, and the range is 34.9°. Both stations show that the number of apparent deflections in the NS direction is relatively small, while the number of apparent deflections in the EW direction and NE directions is relatively large. The calculation results of the observed data from the national earth tilt network indicate that there are 266 components with an apparent deviation angle PS<10°, accounting for 37.20%, the number of components with an apparent deviation angle of PS<22.5° is 445, accounting for 62.24%, and the number of components with PS>45° is 111, accounting for 15.52%; the number of components with apparent deviation angle dispersion error MPS<10° is 247, accounting for 34.55%, the number of MPS<22.5° is 446, accounting for 62.38%, and the number of components with MPS>45° is 43, accounting for 6.01%. Based on the results of this study, we recommend that the initial azimuth angle of the measurement component with an apparent deviation number greater than 20° should be emphatically checked; also we should carefully screen the observation data of the measurement component with an apparent deviation angle dispersion error MPS>20°.
LIU Jinrui,SHEN Xuzhang,TANG Jiu’an et al. A Preliminary Study on the Temporal and Spatial Characteristics of the Apparent Deflection Angle of Earth Tilt Deformation Stations Mainland China[J]. jgg, 2024, 44(2): 202-208.
LIU Jinrui,SHEN Xuzhang,TANG Jiu’an et al. A Preliminary Study on the Temporal and Spatial Characteristics of the Apparent Deflection Angle of Earth Tilt Deformation Stations Mainland China[J]. jgg, 2024, 44(2): 202-208.