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Vertical ocean loading amplitudes from VLBI measurements
Author(s) -
Sovers O. J.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl02648
Subject(s) - very long baseline interferometry , amplitude , geodetic datum , geodesy , geology , physics , optics
Vertical ocean loading amplitudes are determined by analysis of IRIS geodetic VLBI data. The 4 nearly diurnal ( K 1 , P 1 , O 1 , Q 1 ) and 4 nearly semidiurnal ( K 2 , S 2 , M 2 , and N 2 ) component amplitudes can be inferred from the data with accuracies of 1–2 mm. Uncertainties of total displacements can approach 1 cm. Empirically determined total displacements are considerably larger than the values calculated from two geophysical models. The Scherneck model is found to give a better representation of VLBI delay data than the model of Pagiatakis by about 3 mm in residuals at 6 sites. Empirical estimation of the ocean loading amplitudes reduces χ 2 by 3067 for the 96 additional degrees of freedom in a fit to 273,000 IRIS VLBI observations, and reduces the RMS residuals by 3 mm relative to a fit using the fixed Scherneck model. Vertical ocean loading amplitudes can thus be inferred from VLBI data at a level which improves the overall model, but detailed assessment of individual tidal components is presently obscured by incomplete modeling at the tidal frequencies.