As a consequence of continental plate movement, the Earth's surface near active faults deforms before, during and after earthquakes. Similarly, the ground surface near active volcanoes also deforms as a consequence of eruptions and volcano evolution. Crustal deformation can be observed as relative movement of points on the Earth's surface, ground tilt, ground strain, and fault slip (creep). We routinely measure these and other parameters that reflect this deformation.

Global Positioning System (GPS) Observations
Velocities, time series, and maps for stations observed with GPS.

Deformation and Stress-Change Modeling and Monitoring
Geodetic modeling using GPS and InSAR. Earthquake stress triggering and stress transfer analyses.

Modeling the Tectonic Deformation of Western North America through Time
Quicktime animations showing the faulting history of the western United States and northwestern Mexico from 30 million years ago to the present.

Real-time Fault Monitoring Data
The USGS monitors fault activity with strain meters, creep meters and other geophysical instruments. (Note: This link takes you to some new pages. The pages that were formerly linked here, can be found by following this link. 2001-09-20)

San Francisco Bay Area Mini-Plate Boundary Observatory (miniPBO)
The Mini-Plate Boundary Observatory, expands the existing network of San Francisco Bay Area sites instrumented to measure deformation within the seismically active zone of the tectonic plate boundary between the Pacific and North American plates.

Two-color Electronic Distance Meter (EDM)
Results from measuring changes in distances using a two-color EDM. Measurements are made in Parkfield, Long Valley, and Southern California.

Long Valley
Long Valley, in eastern California, is the center of continuing volcanic activity and moderate earthquakes. The USGS monitors geophysical activity in the area. This page contains links to many of the instruments.