9312577 Segall This award provides 52 per cent of the cost of acquiring four new Global Positioning System (GPS) receivers and of upgrading four older generation receivers so that they will be capable of positioning with an accuracy in the millimeter range. The receivers are to be used for accurate geodetic measurements in research projects of the crustal dynamics group in the Department of Geophysics at Stanford University. The University is committed to providing the remaining funds needed for the acquisition and upgrade. The Global Positioning System, when utilized with state-of- the-art receivers and data processing methods, is capable of measuring horizontal and vertical motions of the continental crust with sub-centimeter precision. GPS will be used by the Stanford group to measure plate tectonic motion, strain build-up near active faults, displacement due to earthquakes, deformation associated with volcanic activity, and subsidence due to underground fluid extraction. ***