摘要
全球超导重力观测可以提供地球重力场多时间尺度的变化信息,从几秒到几十年不等.在亚十年尺度,地表重力变化主要来自于地球外部流体效应和深部长周期运动,前者可以基于最新全球模型和观测数据来确定,后者由于对地球深部结构认知不足尚存在很大的不确定性.本研究采用多种频谱方法分析了1996—2019年期间全球可用超导重力残差序列,证实了地表连续重力观测中存在准六年振荡(简称SYO)信号,且利用不同台站观测序列提取的重力SYO振幅范围约在0.5~0.7μGal之间.与构建的SYO时变重力模型相比,有限台站的观测数据显示重力SYO仍然具有球谐Y2,2模式的空间分布,尤其是在相位方面.不同台站观测与建模信号之间的振幅转换因子均超过固体潮、大气和海潮负荷的相应值,进一步分析全球水文模型和实测数据,结果表明重力SYO不太可能来自地球外部流体效应.尽管学界普遍认为准六年振荡源于地核运动,但其地表重力和位移观测振幅与现有理论模型的预测结果差异依然显著,表明其实际动力学过程可能比以往的机制解释更复杂,对地球准六年振荡的溯源还需进一步研究.
Global superconducting gravity observations can provide variational informations about Earth′s gravity field on multiple time scales,ranging from seconds to decades.On the intradecadal scale,surface gravity variations mainly arise from Earth′s external fluid effects and deep interior long-period motions.The former can be determined based on the latest global models and in-situ observational data,and the latter is subject to large uncertainties due to a lack of knowledge of the Earth′s deep structure.This study analyzed the available superconducting gravity residual sequences across the globe over the long period of 1996—2019 using diversified spectral methods,and confirmed the existence of a quasi-six-year oscillation(referred to as SYO)signal in surface continuous gravity observations.The amplitudes of gravity SYO recovered from the observation sequences at different stations range from 0.5 to 0.7μGal.Compared with the constructed time-varying gravity model of SYO,the observations from the limited stations show that the gravity SYO still has a spatial distribution of spherical harmonic pattern Y2,2,especially in terms of phase.The amplitude transfer factors between the observed and modeled SYO signals at different stations surpass the corresponding values for the solid tides,atmospheric loading and ocean tide loading,and further analyses of global hydrological models and in-situ observations show that the gravity SYO is unlikely to originate from Earth′s external fluid effects.Despite the prevailing belief that the quasi-six-year oscillation originates from core motion,the observed amplitudes of surface gravity and displacement deviate significantly from the predicted results of existing theoretical models,indicating that its actual dynamic process may be more complicated than previous mechanism explanations,and further research is needed to trace the source of Earth′s quasi-six-year oscillation.
作者
栾威
丁浩
邹传义
申文斌
LUAN Wei;DING Hao;ZOU ChuanYi;SHEN WenBin(School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China;Wuhan Gravitation and Solid Earth Tides National Observation and Research Station,Wuhan 430071,China)
出处
《地球物理学报》
北大核心
2025年第9期3314-3327,共14页
Chinese Journal of Geophysics
基金
国家自然科学基金(42204003,42274011,42388102,42374033)
湖北珞珈实验室专项基金(220100002)
武汉引力与固体潮国家野外科学观测研究站开放研究基金(WHYWZ202206)联合资助.
关键词
超导重力观测
准六年振荡
频谱分析
外部流体源
地核运动
Superconducting gravity observations
Quasi-six-year oscillation
Spectral analyses
External fluid sources
Core motion
