Correctives to the scheme of the Earth's structure inferred from new data on nutation, tides, and free oscillations

摘要

When analyzing the new high-accuracy observations of the forced nutation and tidal variations in the acceleration of gravity, it was found that they are in sharp contradiction to the present-day models of the Earth's interior based on seismic data and the data on the periods and damping constants of the free oscillations of the Earth. The elimination of these contradictions requires analyzing the uniqueness of the interpretation of the free oscillations of the Earth, taking into account the new data. Below, I present the initial results of solving the inverse problem of constructing radially symmetric frequency-dependent models of the Earth's internal structure, which are most consistent with the entire set of recent data on the amplitudes and phases of tides, forced nutation, and the periods and damping of free oscillations. The misfits were minimized by the method of steepest descent in the space of parameters determining the density (provided that the total mass and moment of inertia do not change) and the creep function at different depths. The constructed models are much more consistent with the observations not only within the entire interval of periods ranging from 1 s to 14 months, but also within narrower intervals. However, I note that the PREM model for the period of oscillations of 1 s remains almost the same (the travel-time residuals of the body waves are smaller than the errors of observation).