. 24/7 Space News .
GPS Satellite Receivers Found To Be New Tool For Earthquake Studies

a very expensive "seismograph"
Boulder - May 19, 2003
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.

"This is the first time GPS has been used to track seismic waves," Larson said. "The signals were large enough to be recorded by GPS receivers as far away as Colorado Springs, Colorado."

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.

"The nice thing about GPS is it's great versatility," said Larson. "In this study we were able to track seismic waves that traveled from Alaska through Canada to Washington, Montana and Colorado."

GPS also has a number of other scientific uses, like measuring ice sheet movements, the inflation of magma under volcanoes and plate tectonics, Larson said. More practical uses of GPS include navigating aircraft, boats and cars, as well as helping lost hikers find their way to safety.

GPS users -- like hikers, boaters and car drivers -- decide how frequently their position determination is needed. For measuring seismic waves from Denali, Larson's team used GPS receivers that were set to measure positions once each second, or 1 Hertz.

Ordinarily, she said, scientists study earthquakes with seismometers, but these often are set for a particular sensitivity range. Because the earthquake in Alaska was so big, however, many seismometers in the United States and Canada were not able to measure it. "But GPS researchers love very big signals," Larson said. "The bigger the better for us."

The Denali quake ruptured almost 200 miles, causing surface displacements of more than 25 feet in some places, she said. "This is permanent deformation. The deformations we observed with GPS in the lower 48 states also were large, but were caused by the seismic waves and did not cause permanent displacement."

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, she said, and scientists use them primarily to monitor small motions on faults. Roughly 250 GPS receivers are operating in Los Angeles County, for example, installed in response to the 6.7 magnitude 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.

Related Links
Earthscope
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

A Fiery Debate About Volcanoes
Berkeley - May 14, 2003
In a Perspective in the May 9 issue of Science, geochemist Don DePaolo and geodynamicist Michael Manga defend a fundamental assumption of Earth science, the mantle plume model of hotspots, against an outbreak of seismic skepticism.



Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only














The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.