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Central Washington University

Whole Lotta Shakin' Goin' On

Whole lotta shakin’ goin’ on, or  at least that’s Tim Melbourne’s take on the world. Melbourne, a professor of geological sciences, analyses more than 400 individual Global Positioning System (GPS) sensors scattered around the Pacific Northwest, tracking infinitesimal movements of the Earth’s crust. These sensors, encased in concrete and lodged in bedrock, transmit vital information to his geodetic laboratory in Ellensburg, information that may subtly predict when the Big One will take place.

 

According to Melbourne and other earthquake specialists, the Pacific Northwest is ripe for a massive quake, forecast to measure up to 9 on the Richter scale, that could devastate an area extending from Vancouver, British Columbia to northern California. This area, known as the Cascadia Subduction Zone, has a history of extraordinary earthquakes, judging from the geological record and Native American stories.

 

The Cascadia Subduction Zone (or Cascadia fault) is result of two the Juan de Fuca and the North American tectonic plates that grind against each other. The Juan de Fuca plate creates new ocean floor off the Washington and Oregon coasts that pushes against and beneath the continental shelf.  As more material wells up along the ocean ridge, the ocean floor moves toward and beneath the continent. The North American Plate also moves and overrides the oceanic plate. The Cascadia Subduction Zone is where the two plates meet and lock.

 

“We can track gradual changes in a certain direction as one plate moves forward,” said Melbourne, whose equipment is so sensitive can track the sensors’ movement to the millimeter. “What indicates a brewing seismic event is the steady, year-in year-out compression of the continental crust throughout the Pacific Northwest.  ‘push back’ as the sensors’ position suddenly reverses.”

 

Eventually, as the song says, “somethin’s gotta give.” Mounting pressure between the two plates eventually will cause the fault connecting them to break and slide suddenly up to 60 feet, producing a catastrophic earthquake and tsunami. The coastal areas of western Washington and Oregon will receive the brunt of such a quake and the resulting tsunami could reach heights of 100 feet, which would destroy seaside communities. The tsunami from the last such Cascadia event, in AD 1700, propagated across the Pacific ocean and killed thousands in Japan.

 

With this in mind, NASA, the USGS, and the National Science Foundation selected CWU to develop an early-warning system for earthquake and tsunamis. The Pacific Northwest Geodetic Array (PANGA) is the only research facility in the state focused exclusively on measuring, monitoring, and mitigating Washington’s natural hazards with Global Positioning System (GPS) technology. Melbourne, the director of PANGA activities, recently received a $1.2 million grant to upgrade the system. 

 

CWU, a good 100 miles and a mountain range away from Seattle, was chosen as the most viable spot for the lab, since it will remain functioning after a major earthquake and scientists can continue to send critical data to first responders. This is in contrast to the failure of the seismic network at the University of Washington after the 2001 Nisqually Earthquake. The Nisqually quake only registered 6.8 on the Richter scale, 5,000 times smaller than the magnitude 9 earthquake now building just thirty miles below Puget Sound.