Geodesy by radio interferometry: Evidence for contemporary plate motion

Abstract

Analysis of 211 very long baseline interferometry observing sessions carried out between November 1979 and August 1984 has yielded estimates of the distances between various radio telescopes located inNorth America and Europe. The average rate of change of the distances between four radio telescopes in North America (Haystack Observatory, Massachusetts' Westford Radio Telescope, Massachusetts; George R. Agassiz Station, Texas' and Owens Valley Radio Observatory, California) and one in Europe (Onsala Space Observatory, Sweden) obtained from the analysis of these data is 19 + 10 mm/yr, where the (68% confidence interval) standard deviation is for the estimate of the rate of change of the Haystack-Onsala baseline length, the one determined most accurately from these data. This estimate of the standard deviation is dominated by the effects of correlated systematic errors due mostly to enors in the model used for the atmospheric delay which we infer introduces errors in each baseline length estimate of 40 mm standard deviation and 60 days correlation time. (By contrast the statistical standard deviation is only 2 mm/yr.) The estimated geologic rates of change of these baseline lengths, averaged over • 10 6 years, are 15 to 17 + 3 mm/yr for the various North American sites to Onsala. Improvements in our model of the atmosphere, and continued monitoring of the distances between North American and European telescopes, will allow the uncertainty of the rate estimates to be reduced over the next few years to a value small compared to our estimated rate of change of these baseline lengths. The use of multiple radio telescopes in Europe will allow us also to separate possible local site motions from plate motions. Paper number 5B5628. 0148-0227/86/005 B-5628 $05.00 and (2) to present the results for the baseline length estimates, their rates of change, and their uncertainties. The effects of the earth's atmosphere on the accuracy of these results are considered in detail by Davis et al. [1985]. 2. MATHEMATICAL AND STATISTICAL MODELS S-439 00 Onsala, Sweden.

Interferometer Techniques for Astrometry and Geodesy

“…In addition to solid-Earth tides, displacement of land masses resulting from tidal shifts of water masses, called ocean loading, is measurable. The earliest evidence of contemporary motion of tectonic plates was found by Herring et al (1986), who reported that the increase in the baseline between Westford, MA, and Onsala, Sweden, based on data from 1980 to 1984, was 17˙2 mm/yr. A plot of the extensive measurements of the Westford-Onsala baseline is shown in Fig.…”

Introduction and Historical Review

“…An important result of this effort has been the establishment of the International Celestial Reference Frame adopted by the IAU, which is based on 295 "defining" sources whose positions are known to an accuracy of about 40 as (Fey et al 2015). Another striking result of the geodetic VLBI work has been the detection of contemporary plate motions in the Earth's mantle, first measured as a change in the Westford-Onsala baseline at a rate of 17˙2 mm/yr (Herring et al 1986). The VLBI measurements of plate motions is shown in Fig.…”

Application of Space Techniques to Geodesy and Geodynamics in Japan.

“…By 1992, several mobile sites have been occupied by GSI to control geodetic networks in Japan with unprecedented high accuracies (Tobita et al, 1993); these studies have detected plate motions (Matsuzaka et al, 1991). (Herring et al, 1986). Figure 2 shows the baseline length change in the Kashima-Kauai baseline for data obtained from 1984(Ryan et al, 1993 (Ryan et al, 1993).…”

“…Progress in Earth rotation studies (e.g., Tapley et al, 1985;Campbell et al, 1987) and determining a terrestrial reference frame (e.g., Boucher et al, 1993) in geodesy and detection of plate motion (e.g., Christodoulidis et al, 1985;Herring et al, 1986;Heki et al, 1987) in geodynamics are the most eminent examples.…”