Body tides on a 3-D elastic earth: Toward a tidal tomography

The deformational and gravitational response of the Earth to the tide generating potential has generally involved 1-D (i.e., depth varying) Earth models. Progressive improvement in observational constraints on body tides, generated from both ground and space-based surveys, suggests that an examination of the potential impact of lateral variations in Earth structure is warranted. We present a suite of predictions of the body tide response within the semi-diurnal, diurnal and long-period tidal bands computed using a finite-volume numerical code. The calculations adopt 3-D density and elastic structure taken from seismic inferences and, in a subset of the calculations, dynamic topography on the surface and internal interfaces. We find that perturbations in the radial displacement and surface gravity within the semi-diurnal band reach ~ 1 mm and 0.15 µgal, respectively. The perturbations in the diurnal band are comparable to these values, and within the long-period band they are a factor of 3–5 smaller. We also demonstrate that lateral variations in the elastic moduli, which have been ignored in recent work, contribute greater than 50% of the total perturbation. The level of perturbation associated with 3-D structure exceeds the current observational uncertainty obtainable using space-geodetic methods, and this suggests the possibility of performing tidal tomographic inversions of such data.