Present tectonic-plate motions from lunar ranging

Abstract

Measurements to determine the motion of the Pacific Plate with respect to North America are planned to start within a few months. The University of Hawaii Lunar Ranging Station on Maui is expected to begin operating, and to achieve an accuracy of 2 or 3 cm soon for a single run. The University of Texas McDonald Observatory has been achieving an accuracy of 8–15 cm on a routine basis since late 1971. Work on further improving the McDonald accuracy is planned. Using data from many runs, an accuracy of 1 cm/yr is expected for the relative motion within the first few years. A transportable lunar-ranging station has been proposed which could be constructed in about eighteen months. The station could observe for 3–6 weeks at a chosen site, and determine the location of the site with respect to the fixed lunar-ranging stations. The accuracy expected is 1–3 cm in each coordinate. If approved, a possible initial itinerary for the station might be as follows: 1. (a) two or three sites in California, including Goldstone, plus one site in Utah; 2. (b) sites in Baja California and Mexico, plus several others in the U.S.; 3. (c) several sites in Central America, the Caribbean, and South America; 4. (d) repeat measurements in California, Utah, and Baja California, plus initial measurements at sites in Africa, India, and the Pacific. It is expected that data on plate motions also will become available from satellite range measurements and VLBI.