Ten million dollars in grants from the W.M. Keck Foundation ($5.6 million), the National Aeronautics and Space Administration ($2.4 million), and the National Science Foundation ($2 million) will make Southern California the best-surveyed area on the planet and provide a powerful tool for scientists seeking to understand the region’s earthquake potential.
The grants were announced on Feb. 12 by the Southern California Earthquake Center (SCEC), headquartered at USC.
SCEC provides oversight and coordination for the Southern California Integrated GPS Network (SCIGN), which will use the new funds to expand, from 45 to 250 sites, an array of ground-based “monuments” that are used to electronically track satellites of the Global Positioning System (GPS). GPS, a constellation of 24 navigation satellites operated by the U.S. Department of Defense, permits points on the Earth’s surface to be located with high precision.
The expanded monument network will enable scientists to follow, in unprecedented detail, movements of the Earth’s crust in one of the world’s most seismically active and heavily populated areas.
“Thanks to the W.M. Keck Foundation, NASA and NSF, the Southern California scientific community can pioneer the use of the most promising new tool in geophysics since the invention of the seismometer,” said SCEC director Thomas Henyey, who announced the grants at a special meeting of the SCIGN coordinating committee. “Eventual completion of the 250-station array will put the full potential of GPS technology to work in an earthquake-prone region particularly suited to the task,” said Henyey, a professor of earth sciences.
“GPS makes it possible to measure the position of the monuments with extraordinary accuracy,” said Mike Watkins of the Jet Propulsion Laboratory. “Although the monuments may be separated by scores of miles, a change in their relative positions of no more than a 16th of an inch can be detected by the GPS system.”
In seismically active areas such as Southern California, where plate tectonic forces are at work, substantial earth movements of 1 inch per year occur continuously and are easily measured by the state-of-the-art GPS technology.
“These movements give scientists indications of how fast strain is building up, where it’s concentrated, and where earthquakes might occur in the near future,” noted SCIGN chairman William Prescott of the U.S. Geological Survey (USGS).
The array, which started with only four sites in 1990, has already detected very small motions of the Earth’s crust in Southern California – motions associated with the 7.3 1992 Landers and 6.7 1994 Northridge earthquakes.
“The GPS receivers operating during the Landers earthquake were able to detect, for the first time, subtle changes in the regional deformation pattern. Such changes are potentially of great importance for studying the physics of earthquakes and hazards mitigation,” said Yehuda Bock, director of the Scripps Orbit and Permanent Array Center at UC San Diego’s Scripps Institute of Oceanography.
“Before and after the January 1994 Northridge earthquake, the few GPS monuments then in service revealed important scientific clues about the processes taking place far underground,” said Ken Hudnut of USGS in Pasadena. “GPS technology is particularly valuable for studying hidden faults, like the one that caused the Northridge earthquake. Faults located far underground are more difficult to study by other methods.”
The current network was funded by earlier grants from NASA and NSF to the Jet Propulsion Laboratory and the Scripps Institute of Oceanography and by USGS. According to SCEC science director David Jackson of UCLA, SCIGN will use the funds to rapidly expand the network of receiver stations.
“In addition to providing general coverage for the entire 25,000-square-mile area extending from the Tehachapi Mountains south to the Mexican border, and from the Pacific Ocean to the Colorado River, stations will be concentrated along a tectonically critical corridor extending through the Los Angeles basin. Each station will be monitored daily,” Jackson said.
SCIGN is currently operated by three primary institutions – the Jet Propulsion Laboratory, UC San Diego’s Scripps Institute of Oceanography and USGS – with participation by other SCEC institutions and local and state government agencies.
The Keck Foundation, NASA and NSF funds also will be used to support data collection, processing and archiving by the three main SCIGN participants. They in turn will make the processed data available to the entire scientific community, where it will be combined with data from other sources to create the most accurate and detailed picture ever of the earthquake hazard in Southern California.
Established in 1991, SCEC is an NSF Science and Technology Center funded by separate grants from NSF and USGS. “The center was conceived with the idea that a better understanding of earthquakes in Southern California will help protect the lives and property of the more than 15 million people living here,” Henyey said.
Working in partnership with USGS and the Jet Propulsion Laboratory, the center includes distinguished faculty members from six core academic institutions – Caltech, Columbia University’s Lamont-Doherty Earth Observatory, UC Santa Barbara, UCLA, UC San Diego’s Scripps Institute of Oceanography, and USC.