San Francisco Bay Region Crustal Deformation Measurements

On the basis of research conducted since the 1989 Loma Prieta earthquake, U.S. Geological Survey (USGS) and other scientists conclude that there is a 70% probability of at least one magnitude 6.7 or greater quake, capable of causing widespread damage, striking the San Francisco Bay region before 2030. Major quakes may occur in any part of this rapidly growing region. With numerous faults in close proximity to a large urban population, the San Francisco Bay area area has one of the highest earthquake hazards in the world. Many instruments are deployed to study deformation in this area.

Plots of Current Data

For most instruments, measurements are made and sent to computers several times each hour. To see these data, choose among the following:

DISCLAIMER: 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.

Data for the Last 7 Days

• Plot Dilatational Strain Measurements
• Plot DTM Tensor Strain Measurements
• Plot GTSM Tensor Strain Measurements
• Plot Creep Measurements
• Plot Tilt Measurements
• Plot Environmental Data

Data for the Last 30 Days

• Plot Dilatational Strain Measurements
• Plot DTM Tensor Strain Measurements
• Plot GTSM Tensor Strain Measurements
• Plot Creep Measurements
• Plot Tilt Measurements

Long-Term Data

• Plot Dilatational Strain Measurements
• Plot GTSM Tensor Strain Measurements
• Plot Creep Measurements
• Plot Tilt Measurements

Quick View of Data for all Regions

Complete List of Instruments for the San Francisco Bay Area

Instruments Located in the San Francisco Bay Area

Map of Instrument Locations

• Creepmeters

Creepmeters continuously monitor near-surface fault movement on the actual fault traces to characterize the rate and nature of fault slip. They can detect changes of about 0.1 millimeters.

 

• Dilational Strainmeters

These instruments measure the volumetric stretching and squeezing of the ground near active faults. Over short time periods they can detect changes of 1-part-per-billion (1 inch in 16,000 miles).

 

• Tensor Strainmeters

These instruments measure the directional stretching and squeezing in the ground near active faults. Over short time periods they can detect changes of 1-part-per-billion (1 inch in 16,000 miles).

 

• Tiltmeters

Tiltmeters continuously monitor rotation or tilting in the ground near active faults by precisely measuring either the movement of a pendulum or fluid levels in connected reservoirs (rather like the ring in a bathtub) as the ground tilts. Measurements can easily be made to better than 1 part per billion.

 

• Geodesy

The location of many land survey markers located in active fault zones in the United States are measured using Global Positioning System (GPS) receivers. These receivers are a high precision version of the small handheld receivers available today in electronics stores.The high precision version together with appropriate computer processing is capable of measuring the horizontal position of sites with an accuracy of a few millimeters (mm), and the vertical position with an accuracy of about 10 mm. Using GPS, relative motion of sites a few hundred kilometers apart can be determined to a precision of 1 part per 10 million, and relative motion of sites on opposite ends of the continent to a precision of 1 part per billion. The U.S. Naval Observatory maintains a site containing general information on the GPS system.

 

• Pore Pressure Monitors

These instruments record fluid pressure changes in deep boreholes driven by fault activity Measurements can be made to beter than 0.1 mbar.