Geodesy and Gravity/Tectonophysics
Study of harmonic site position variations determined by very long baseline interferometry
Article first published online: 8 APR 2003
Copyright 2003 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 108, Issue B4, April 2003
How to Cite
2003), Study of harmonic site position variations determined by very long baseline interferometry, J. Geophys. Res., 108, 2190, doi:10.1029/2002JB001801, B4., and (
- Issue published online: 8 APR 2003
- Article first published online: 8 APR 2003
- Manuscript Accepted: 26 AUG 2002
- Manuscript Revised: 5 AUG 2002
- Manuscript Received: 30 JAN 2002
 Position variations of 40 very long baseline interferometry (VLBI) stations at 32 tidal frequencies were obtained from analysis of 3 million measurements of group delays from 1980 to 2002. Residual displacements after the removal of the effect of solid Earth tides were studied. The purpose of this study is to investigate a harmonic signal at any frequency where it is expected and to assess quantitatively whether the models of vertical and horizontal site position variations agree with the observations. It was found that the estimates of station displacements are generally in good agreement with the ocean loading computed on the basis of ocean tide models for the main diurnal and semidiurnal tides. Moreover, VLBI results allow us to discriminate between different ocean tide models. However, discrepancies between VLBI results and all models of ocean loading for K1, K2, and S2 tides exceed both the errors of the VLBI estimates and the errors of ocean loading displacements based on the reported formal uncertainties of ocean tide models. It was found that there is a significant nontidal signal at diurnal and annual frequencies. Applying a model of hydrological loading reduces the variance of the residual vertical displacements at the annual frequency by 30%. Using an empirical model of harmonic site position variations in VLBI processing provides a better fit and improves the baseline length repeatability.