A Qualitative and Quantitative Comparison of Geodetic Results from SLR and VLBI

Abstract

During the past decade, both Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) systems have occupied the same, or nearly the same, locations on the surface of the Earth. Two of the commonly used geologic models which describe the plate geodesic rates between locations on the Earth’s surface are the AMO-2 and the NUVEL-1.Qualitative results indicate that both the SLR and VLBI measure motion between Monument Peak and Quincy to be about — 26 mm/yr, which is much less than predicted by either the AMO-2 (- 53.3 mm/yr) or the NUVEL-1 (- 45.4 mm/yr) geologic models. SLR and VLBI measure extension within the North American plate in the Basin and Range province of the Western United States. Both technologies measure the widening of the North Atlantic to be about 20% less than predicted by either the AMO-2 or the NUVEL-1 models.Quantative results have been obtained for six locations which have been occupied by both the SLR and VLBI systems for an adequate time period to enable the calculation and comparison of the intersite geodesic rates for the two technologies. These six locations are: Platteville, Co, Quincy, CA, and McDonald, TX, on the North American plate; Monument Peak, CA, and Maui, HW on the Pacific plate; and Wettzell, FRG, on the Eurasian plate. For the 15-geodesic rates between these sites, the mean difference between SLR and VLBI (SLR minus VLBI) is — 0.2 mm/yr with a standard deviation of 5.2 mm/yr (- 0.2 ±5.2 mm/yr). Similar values between SLR and AM0–2 are 0.6 ± 10.9 mm/yr and between VLBI and AM0–2 are 0.4 ± 8.8 mm/yr. For the SLR and NUVEL-1, the value is 0.6 ± 9.1 mm/yr; and for VLBI and NUVEL-1, the value is 0.4 ± 7.0 mm/yr. For the above data set, the SLR and VLBI derived-tectonic rates show better agreement with each other than with either the AM0–2 or the NUVEL-1 geologic models.