9619201 Bock This award supports research aimed at an integration of two technologies which have proven useful for monitoring motion of the Earth's crust. The Global Positioning System (GPS) is currently capable of measuring baselines (the distance between two GPS receiver location points on Earth) with a precision in the millimeter range at distances of hundreds of kilometers. Interferometric Synthetic Aperture Radar (INSAR) cannot offer a comparable level of precision, but has the advantage of being able to measure relative motion of the crust over a continuous area (as opposed to a limited number of discrete points on the surface). Combining the two approaches will provide greatly enhanced capabilities for understanding such phenomena as earthquake related motion (pre-, syn-, and post-seismic), volcanic activity, plate tectonic motions, groundwater movement, and other local and regional crustal strain processes. The research is a collaboration among geoscientists at the University of California, San Diego, Stanford University and the University of Hawaii. The approach by the collaborators will be: (1) to reduce the so-called orbital or baseline error of INSAR by deploying radar reflectors or transponders at selected GPS receiver sites and thereby pin down the precise locations of those points to serve as anchors for the INSAR interferometry, and (2) use meteorogical models and satellite data to reduce the error in GPS locations due to the effect of water vapor in the atmosphere. ***
