ALBERT

Description: GNSS observations of M〈sub〉2〈/sub〉 ocean tide loading horizontal displacements (OTLHD) at 256 stations in western Europe generally show amplitudes of less than 10 mm. When compared to predictions using the standard Earth model PREM and the high-resolution ocean tide model TPXO9v5, they show discrepancies (or residuals) greater than 0.4 mm at most of these GNSS stations. This can be due to uncertainties in ocean tide models or deviations in the Earth’s internal structure. To assess the former, we computed the predicted OTLHD across western Europe using the recent global ocean tide models DTU10, FES2014b, GOT4.10 and TPXO9v5. It is found that the inter-model standard deviation is under 0.2 mm at all but 18 and 30 stations (less than 10% of all stations), respectively, for the West and South displacements, and the mean size of the standard deviations is less than 0.16 mm. Therefore, it is necessary to look into the structural deviations of the Earth from those revealed by PREM. Here, using both one-dimensional (1-D) and recently developed three-dimensional (3-D) Earth models, we investigate the effect of structure variations of the Earth’s lithosphere and mantle on OTLHD. In particular, given that lateral heterogeneity induces an additional toroidal displacement, we explore if the presence of lateral inhomogeneity in the mechanical structure, characterized by elastic moduli, can reduce the discrepancies in horizontal displacement.