Tectonic Plate Motion
By determining the relative 3-dimensional position of globally distributed telescopes to a precision of a few millimeters, motions of the Earth's tectonic plates can be directly measured. A 10-year time history of the distance between the Westford antenna and an antenna in Germany shows that the separation of North America and Europe is proceeding at a steady rate of about 17 millimeters per year. Global tectonic motions measured by VLBI also allow scientists to measure changes in the position of the famous San Andreas fault in California, where the Pacific plate slips past the North American plate at the rate of about 5 centimeters per year.
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