PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASEOctober 28, 1996
NEW TECHNOLOGY WILL HELP TO MEASURE AND STUDY EARTHQUAKES
Scientists have begun installing a network of 250 Global
Positioning System (GPS) receivers that will continuously measure
the constant, yet physically imperceptible, movements of
earthquake faults throughout Southern California. This
information, which in many cases will be gathered and analyzed
with the help of local students, should help researchers forecast
future earthquake hazards in the greater Los Angeles area.
NASA Administrator Daniel S. Goldin dedicated a new site in
the Southern California Integrated GPS Network (SCIGN) today at
Rialto High School, before a demonstration of the technology to
science students from the school. Goldin was accompanied by U.S.
Rep. George Brown (D-Calif.), the ranking minority leader of the
House Science Committee, and representatives from the National
Science Foundation and the U.S. Geological Survey.
"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 that are jointly governed by the departments
of Defense and Transportation. The satellites are arranged so
that several of them are "visible" from any point on the surface
of the Earth at any time. A user on the ground using a GPS
receiver can determine the site's precise location by
coordinating the signals from the satellites.
"The surface of the Earth is constantly moving and Southern
California is being squeezed in the process. The GPS network will
continuously measure movements of the Earth's 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 NASA's Jet Propulsion
Laboratory (JPL), Pasadena, CA.
"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.
"Continuous GPS measurements will also allow for more rapid
regional damage assessment following large earthquakes."
The earthquake network began in 1990 with only four GPS
receivers as a prototype project funded by NASA. It detected
very small motions of the Earth's crust in Southern California
associated with the June 1992 Landers and the January 1994
Northridge earthquakes. "The GPS receivers operating during the
Landers earthquake were able to detect for the first time a
subtle change in the regional deformation pattern, which is
potentially of great importance for studying the physics of
earthquakes and hazards mitigation," said Dr. Yehuda Bock, a
SCIGN executive board member from Scripps Institution of
Oceanography, University of California, San Diego.
Currently, the SCIGN has 40 GPS receivers up and running,
with the remaining receivers scheduled to 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," JPL's Donnellan said. "We will try to determine if other
faults have been loaded as a result of the earthquake."
"The survey data are particularly important for identifying
active buried faults that do not reach the ground surface. Such
faults may be common in the Los Angeles metropolitan region,"
said Dr. David Jackson, science director of SCEC.
The GPS measurements will also be useful to characterize
earthquake damage. "The network will help agencies monitor
important structures. GPS receivers placed on or near dams,
bridges and buildings would allow off-site detection of probable
damage to those structures. We are collaborating with Los Angeles
County in a pilot study of continuous GPS monitoring of Pacoima
Dam," said Dr. Ken Hudnut, SCIGN executive board member at the
U.S. Geological Survey in Pasadena.
Many of the receivers are being placed at schools so that
students can be involved in the experiment. SCEC's "Global
Science Classroom" at the University of Southern California has
formed a partnership with JPL, several school districts and
educators' groups to develop a science unit for use in schools.
The unit, titled "The Elastic Planet," will give students access
to the data being gathered by the network.
"This network is a model of interagency cooperation between
NASA, the U.S. Geological Survey and the National Science
Foundation, as well as with local governments and schools,"
Goldin said. "Students will get hands-on science experience in
using real data. It should ignite their enthusiasm for science
while providing a genuine public service."
SCIGN is a consortium of institutions with a common interest
in using GPS for earthquake research and mitigation. The
consortium is coordinated by the Southern California Earthquake
Center (SCEC), a National Science Foundation Science and
Technology Center headquartered at the University of Southern
California. The lead institutions in the installation and
operation of SCIGN are: JPL, the Institute of Geophysics and
Planetary Physics-Scripps Institution of Oceanography at the
University of California, San Diego, the United States Geological
Survey, the University of California, Los Angeles and the
University of Southern California.
Mary Hardin, JPL, Pasadena, CA
October 28, 1996
NASA Headquarters, Washington, DC
National Science Foundation, Arlington, VA
U.S. Geological Survey, Reston, VA
For more information, visit the Global Positioning System home page.