April 16, 2001

Contact: Meghan Miller (509-963-2825/email meghan@geology.cwu.edu)

Scientists from Central Washington University will present the latest findings on the Nisqually earthquake Wednesday (APRIL 18) in San Francisco at the Annual Meeting of the Seismological Society of America.

The most recent global positioning system (GPS) observations indicate displacements that occurred during the quake were smaller than first predicted from the initial seismological data alone, according to Dr. Meghan Miller, CWU geological sciences professor.

GPS data found that Seattle actually moved four millimeters to the southwest and one station in southern Puget Sound moved nine millimeters. Another station at Satsop moved six millimeters to the west-southwest.

"The horizontal motions are also somewhat different than we initially predicted," Miller says. "In the days after the quake, additional data allowed us to correct our preliminary model."

This is the first time that a Pacific Northwest earthquake has been studied using GPS measurements.

"It took several days for enough GPS data to accumulate to make good estimates of post-earthquake station positions," Miller notes. "These observations were used to test the deformation model and found that the actual motions were less than those predicted."

Miller, who coordinates the Pacific Northwest Geodetic Array (PANGA), recently testified before Congress about its use in studying the February temblor. PANGA is a multi-institution collaboration focused on using GPS geodesy for studies of Earth deformation.

In response to the Nisqually quake, PANGA has led installation of seven additional GPS stations in the Puget Sound region with support from the National Science Foundation.

Four new stations are already on-line and three others will be installed over the next several weeks.

"They will allow for more intensified monitoring of the Seattle fault and other faults that cause shallow earthquakes," Miller adds. "Finding stations with a clear sky view and stable ground is a big challenge in the Pacific Northwest."

Individuals and organizations interested in hosting a PANGA GPS base station can find out more at www.geodesy.cwu.edu/.

PANGA is also an important component of a national and international collaboration among scientists called Earthscope, according to Miller.

"This initiative would scale up our national infrastructure for seismic risk monitoring and for basic earth sciences research," she says. "Earthscope has been approved by the National Science Board and now depends on the Congressional appropriations process. If this project is funded, more than 100 new geodetic GPS stations would be installed in the Pacific Northwest."