A high precision radio astronomy system has been adopted and used at the Goddard Space Flight Center in studies of the movement of the earth's crust. Very Long Baseline Interferometry (VLBI) can measure the rotation of the earth, and polar motion, with a current precision of better than 10 cm. Such precise measurements may shed light on the relationship between changes in the earth's orientation and movements in the earth that are associated with large earthquakes. Such movements may occur before an earthquake, but so slowly and over so large a region as to be undetectable by conventional means. Using VLBI stations, the Crustal Dynamics Project has made measurements on the longer baselines to measure continental drift, and on the shorter ones to monitor regional activity.