Volume 5, Number 1     January/February 1997

  Advanced Technologies

Quake Forecast Data With GPS

NETWORK OF 250 NASA GLOBAL POSITIONING System (GPS) receivers will help students and researchers forecast Los Angeles-area earthquakes. Students will help gather and analyze data.

NASA Administrator Daniel S. Goldin recently dedicated a new site in the Southern California Integrated GPS Network (SCIGN) at Rialto High School.

"This network is a tremendous example of how technology developed for space benefits life on Earth. This interagency project will give us detailed information never before available to track the invisible geologic strains and stresses that lie beneath the California landscape," Goldin said. "Such data should give us fresh insight into the forces that produce earthquakes and could one day help reduce the loss of life and property from such disasters."

GPS uses data transmitted from a constellation of 24 Earth-orbiting satellites arranged so several are visible from any point on the Earth's surface at any time. Someone using a GPS receiver can determine the site's precise location by coordinating signals from the satellites.

"GPS is the most important new technology to emerge for the study of earthquakes in decades. This information will permit us to improve our estimates of the regional earthquake hazard in Southern California and to prioritize earthquake mitigation activities, including emergency preparedness and retrofit strategies," said Dr. Tom Henyey, director of the USGS-NSF Southern California Earthquake Center (SCEC) in Los Angeles.

"The GPS network will continuously measure movements of the EarthÕs crust with a precision of one millimeter per year, which will show us where strain is building up," said Dr. Andrea Donnellan, a member of the SCIGN Coordinating Committee at Jet Propulsion Laboratory (JPL).

SCIGN began in 1990 with four GPS receivers as a NASA-funded prototype project. It detected very small motions of the Earth's crust in Southern California associated with the June 1992 Landers and January 1994 Northridge earthquakes.

Currently, SCIGN has 40 GPS receivers operating. The remaining receivers will be installed over the next three years.

"With data from the 40 receivers, we have determined that Southern California has continued to move since the Northridge quake in 1994. This may mean that stress is being relieved in part without earthquakes, which may reduce the overall earthquake hazard," Donnellan said.

GPS data helps identify active buried faults that do not reach ground surface, and GPS measurements are useful in characterizing earthquake damage. Agencies can monitor off-site probable damage to dams, bridges and buildings via receivers placed on or near the structures.

For more information about SCIGN, contact Dr. John Schied at JPL,
Call 818/354-9627, FAX: 818/393-1492, E-mail: john.scheid@jpl.nasa.gov
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