基于三维地球模型的中国大陆重力潮汐因子研究

Study of tidal gravimetric factors in Chinese mainland based on three-dimensional Earth model

潮汐现象是地球对日、月等星体引力的响应,重力潮汐因子对于揭示地球内部结构具有重要作用.中国地震局、中国科学院等自20世纪80年代开始布设首批重力仪,用于研究中国大陆固体潮空间分布特征,到目前为止已建成超过50个台站的重力观测网络.本研究利用该网络的重力潮汐因子观测结果,结合考虑了横向非均匀效应的潮汐理论和三维地球模型,构建了中国大陆及周边地区的重力M_(2)、O_(1)因子分布模型.基于微扰理论,本研究发现P波速度扰动、S波速度扰动、密度扰动及综合效应对重力M_(2)因子影响的幅值范围分别为-0.12%至0.14%、-0.19%至0.17%、-0.08%至0.06%和-0.09%至0.11%(对O1因子的影响为-0.13%至0.28%、-0.27%至0.15%、-0.12%至0.10%和-0.15%至0.05%),影响最显著的区域为喜马拉雅造山带(负值)和华夏古陆东南缘(正值),体现了这些地区的特殊构造.本研究利用最小二乘配置方法对重力潮汐因子的理论值与实测值进行了融合,发现中国大陆及周边地区的重力M_(2)因子幅值范围为1.130至1.175,总体呈现周围低、中心高的特征.重力O1因子幅值范围为1.145至1.195,总体呈现从西北向东南逐渐升高的特征.以上结果可为中国大陆及周边地区重力潮汐因子、地球模型等相关研究提供参考.

Tides are the Earth's response to the gravitational attraction of the Sun,the Moon,and other stars,and tidal gravimetric factors vital for revealing the Earth's interior structure.The tidal potential can be decoupled in�to several components,among which M_(2) and O_(1) are semi-diurnal and diurnal components,respectively,with the largest amplitudes caused by the attraction of the Moon.The China Earthquake Administration and the Chinese Academy of Sciences deployed the first gravimeters in the 1980s to study the spatial distribution characteristics of solid tides in Chinese mainland,and have developed a gravity observation network of>50 stations.In the current study,we utilized these observations,combined with tidal theory,considering the effects of lateral inhomogeneity and three-dimensional Earth models,such as GyPSuM,SPani,SEISGLOB2,SGLOBE-rani,and SAW642ANb,to construct a tidal gravimetric factor model of the M_(2) and O1 components in Chinese mainland and its adjacent zones.The effect of the lateral inhomogeneity on the tidal gravimetric factor was estimated using the perturbation method.The amplitude ranges of effects of the P-wave velocity perturbation,S-wave velocity perturbation,density perturba�tion,and their summation effects on the M_(2) component were-0.12%to 0.14%,-0.19%to 0.17%,-0.08%to 0.06%,and-0.09%to 0.11%,respectively(the effects on the O1 component were-0.13%to 0.28%,-0.27%to 0.15%,-0.12%to 0.10%,and-0.15%to 0.05%,respectively).For the M_(2) and O1 factors,the West Region Block,southwestern Xizang Block,northwestern South China Block,and central North China Block were attributed nega�tive values,whereas the other regions were attributed positive values.For the M_(2) factor,the Himalayan orogenic belt(negative values)and southeastern margin of Cathaysia(positive values)were most significantly affected by lateral inhomogeneity,reflecting the special tectonics of these regions.There was no obvious maximum value for the O1 factor.The least-square-collocation method based on the idea of"remove-recovery"was utilized to combine the observed and theoretical tidal gravimetric factors.The magnitude of the gravimetric factor of the M_(2) compo�nent in Chinese mainland and its adjacent zones ranged from 1.130 to 1.175,with low values around and high val�ues in the center.The magnitude of the gravimetric factor of the O1 component ranged from 1.145 to 1.195,show�ing a gradual increase from the northwest to southeast.The above outcomes can provide references for related stud�ies of tidal gravimetric factors and Earth models in Chinese mainland and neighboring areas.The difference between the observed and theoretical M_(2) factors peaked at the southeastern margin of Cathaysia.The average dif�ference was approximately 0.01,three to four times larger than the variation range of the theoretical M_(2) factor.This difference corresponds to the deviation between the real Earth and the Earth models.The difference between the su�perconducting gravimeter stations varied from 0.001 to 0.004.However,the difference at the gPhone stations com�monly exceeded 0.01.The results show that setting up more high-precision gravimeters is expected to improve the tidal gravimetric factor model for Chinese mainland.