GPS satellite receivers found to be new tool for earthquake studies

GPS satellite receivers found to be new tool for earthquake studies

SHARE

A serendipitous discovery by a University of Colorado at Boulder-led team has shown for the first time that satellite signals from the Global Positioning System are a valuable new tool for studying earthquakes. CU-Boulder Associate Professor Kristine Larson of aerospace engineering sciences said seismic waves from a 7.9 magnitude earthquake in Alaska’s Denali National Park in November 2002 were detected using Global Positioning Satellite, or GPS, receivers as far away as 2,350 miles from the event. The quake also was picked up by scores of GPS receivers in Canada and the United States.
GPS is a constellation of satellites originally designed by the U.S. military to provide precise positions of ships, tanks, airplanes, other military equipment and even people. Currently there are 27 GPS satellites orbiting Earth at roughly 12,500 miles above the planet. A paper on the subject will be published electronically by Science magazine on Science Express May 15. In addition to Larson, co-authors include Paul Bodin from the University of Memphis and Joan Gomberg from the U.S. Geological Survey’s Memphis office. For measuring seismic waves from Denali, Larson’s team used GPS receivers that were set to measure positions once each second, or 1 Hertz. The Denali quake ruptured almost 200 miles, causing surface displacements of more than 25 feet in some places. For a sense of how big the seismic waves were, a GPS receiver in eastern Washington moved nine inches horizontally in just 10 seconds, even though it was 1,500 miles from the Denali earthquake.
There are many continuously operating GPS receivers in the United States. Roughly 250 GPS receivers are operating in Los Angeles County, for example, installed in response to the 6.7 magnitudes Northridge earthquake in 1994. The National Science Foundation recently funded a research project known as Earthscope to study the structure and evolution of the North American continent, Larson said. Earthscope also is designed to decipher what causes earthquakes and volcanic eruptions and as part of that effort, Earthscope engineers will soon be installing 800 additional GPS receivers in the western United States.