The USGS maintains a variety of fault and volcano monitoring sites around the western United States. Instruments at these sites include strainmeters, tiltmeters and creepmeters, as well as other environmental parameters such as temperature and barometric pressure.
The data are collected and monitored to help understand how, when, and why large earthquakes, fault slip and volcanic activity occur. The measurements provide a near real-time record of the related crustal deformation before, during and after events. The goal is to better understand these natural processes, and use these data to reduce the earthquake and volcanic hazards associated with them.
This web site provides data plots and data downloads for many instruments that are concentrated in areas where large earthquakes are likely to occur in California and areas of known volcanic activity. In particular, the USGS has concentrated instrumentation efforts in the San Francisco Bay Area, near San Juan Bautista and Parkfield, and the Long Valley, CA and Southern California regions.
The plots and data on this site are generated automatically and are not reviewed. They should not be used for engineering, legal, or any other critical applications.