As part of the earthquake process, Earth's surface is being deformed as earthquake faults accumulate strain and slip or slowly creep over time. We use GPS to monitor this movement by measuring the precise position (within 5mm or less) of stations near active faults relative to each other. Months or years later, we occupy the same stations again. By determining how the stations have moved we calculate ground deformation.
The USGS Earthquake Hazards Program (EHP) supports GPS data collection throughout the western U.S. through cooperative agreements with Central Washington University, University of California at Berkeley, University of Memphis, and University of Nevada at Reno. We process GPS data that we collect, as well as data from the USGS Volcano Hazards Program (VHP), our cooperator institutions, UNAVCO Inc., and other sources (see a full listing of observing agencies). These results are available on this website as time series of daily GPS positions.
29 Networks on this Map
Google Earth Files
All stations surveyed since 1992: