基于矩阵球谐叠积方法估计Mm和Mf潮波重力潮汐因子及约束下地幔滞弹性参数

Estimating the gravimetric factors of Mm and Mf tidal waves using MSHS method and its constraints on anelastic parameters of the lower mantle

地幔滞弹性参数对理解和认识地球内部动力学过程及能量耗散机制至关重要.目前, 下地幔滞弹性参数主要依赖长周期固体潮和极潮等大地测量观测的反演与约束, 但相应研究结果之间仍存在明显的差异.本文采用高精度的超导重力仪(Superconducting Gravimeter, SG)观测资料对长周期频段的Mm和Mf潮波重力潮汐因子进行估计, 并反演下地幔滞弹性参数.对SG观测资料进行精细预处理, 并扣除多种重力信号及短周期潮波的干扰;采用矩阵球谐叠积方法估计的Mm和Mf潮波的重力潮汐因子分别为1.1589(±0.0011)-0.0006i(±0.0012)和1.1586(±0.0007)-0.0008i(±0.0009).基于估计的重力潮汐因子, 得到5 mHz参考频率的下地幔滞弹性参数f_(r)(ω)和f_(i)(ω), 对于Mm潮波分别为-15.6(±8.7)和4.7(±9.5), 对于Mf潮波分别为-13.2(±5.5)和6.3(±7.1), 最终反演的物质依赖参数α值为0.185(±0.09), 与已有研究中基于卫星激光测距和GNSS观测的研究结果一致, 表明了估值的可靠性.研究可为下地幔滞弹性参数提供约束, 有助于了解地球内部的物理性质以及地球对于潮汐信号的响应特征.

Parameters of mantle anelasticity are crucial for understanding and recognizing the dynamic processes of Earth's interior and energy dissipation mechanism. So far, the anelastic parameters of the lower mantle mainly rely on inversion and constraints of geodetic observations such as long-period body tides and pole tides;however, there are still obvious discrepancies between the released research results. In this study, we use high-precision superconducting gravimeter (SG) observation data to estimate the gravimetric factors of the Mm tidal wave and Mf tidal wave in the long-period frequency band, and further inverse the anelastic parameters of the lower mantle. We finely preprocessed the SG data, and the interference of various gravity signals and short-period tides are removed. After using the matrix spherical harmonic stacking method to those data, the gravimetric factors 1.1589 (±0.0011)-0.0006i (±0.0012) and 1.1586 (±0.0007)-0.0008i (±0.0009) are respectively obtained for the Mm and Mf tidal waves. Based on those estimations and taking 5 mHz as the reference frequency, the anelastic parametersf_(r)(ω)and f_(i)(ω) of the lower mantle are obtained. For Mm tidal wave,f_(r)(ω)and f_(i)(ω) are -15.6 (±8.7) and 4.7 (±9.5), respectively. For Mf tidal wave, f_(r) (ω) and f_(i) (ω) are -13.2 (±5.5) and 6.3 (±7.1), respectively. The revealed value of material-dependent parameters α is 0.185 (±0.09), which is consistent with the results of Satellite Laser Ranging and GNSS observations in existing studies and indicates the robustness of the estimation. Our study can constrain the anelastic parameters of the lower mantle, which can help to understand the physical properties of Earth's interior and characteristics of the Earth's response to tidal signals.