Tidal deformations of the earth from VLBI observations

Abstract

Based on an analysis of the VLBI observations performed in 1985–2010 within the framework of international geodetic programs on global networks of stations, we have obtained statistically significant corrections to the parameters of lunisolar tides—the nominal complex Love/Shida numbers. The new integral (frequency-independent) values of these parameters (in 10⁻⁴) are h ⁽⁰⁾ = (6113 ± 3) − (33 ± 2)i, l ⁽⁰⁾ = (843 ± 1) − (5 ± 2)i for a total tide; h ⁽⁰⁾ = (6106 ± 3) − (10 ± 6)i, l ⁽⁰⁾ = (843 ± 1) − (8 ± 1)i for diurnal tides; and h ⁽⁰⁾ = (6106 ± 3) − (24 ± 3)i, l ⁽⁰⁾ = (843 ± 1) + (3 ± 1)i for semi-diurnal tides. We have detected a new effect of asymmetry in the horizontal tidal displacements in the direction of tectonic motions for 50 VLBI stations. We have determined upper limits for the influence of the frequency-dependent resonance effects whose estimation accuracy is limited by an abundance of close frequencies in their harmonic expansion. The influence of the transfer function for tides on the VLBI observations has turned out to be lower than the measurement accuracy. In future, positional GPS/GLONASS measurements are planned to be used to refine the resonance effects and the transfer function.