Earth Planets Space, Vol. 52 (No. 11), pp. 959-963, 2000LETTER
M. D. Gerasimenko1 and Teruyuki Kato2
1Institute of Applied Mathematics, 690041 Vladivostok, Russia
2Earthquake Research Institute, University of Tokyo, Tokyo, Japan
(Received October 21, 1999; Revised August 9, 2000; Accepted August 9, 2000)
Abstract: The purpose of this research is to provide a new algorithm for fixing the three-dimensional kinematic reference frame of space geodetic stations in which only vertical components of quasi-stable site velocities for every X, Y, Z direction are used. This KRF does not depend upon any geological model and, thus, is free from the hidden errors coming from the uncertainties of the reference plate motion model, errors in survey data of selected sites as reference stations and the misfit between the measurements and the model predictions. The method has been applied to the VLBI data collected during the period from 1979 to 1997 analyzed by NASA. We have used for the analysis the estimated rate of change of 340 baseline vectors between 59 VLBI sites. As it is clear from our numerous experiments, this algorithm gives a fairly stable results which are in a good agreement with the NUVEL-1 NNR plate motion model if we include for fixing of KRF even a few sites (15-20 points). In the worst case our results obtained using various criteria for selection of quasi-stable sites have 1 mm/yr level agreement for all sites in the horizontal and vertical directions. The agreement of our results and the NUVEL-1 NNR model is on the order of a few millimeters per year in each coordinate. The largest discrepancies reach 20 mm/yr in the sites close to the plate boundaries. The uncertainties of vertical direction do not exceed 1 mm/yr for half of the sites. As a final result, we do not find any clear evidence suggesting the change of Earth's radius, which is considerably less than 1 mm/yr.