Seeing Deeply

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As part of the national EarthScope Program headquartered at OSU, UNAVCO engineer Peter Gray installs a GPS station on the north ridge of Mount St. Helens to measure tectonic plate activity. (Photo courtesy of UNAVCO)

December 17, 2008

Researchers put a continent under intense scrutiny

By Lee Sherman and Nick Houtman

"Not since the Lewis and Clark Expedition 200 years ago has there been such a comprehensive survey of the North American continent." - Gregory van der Vink, Terrametrics, Former EarthScope Director

The orbiting Hubble telescope gives humans a window into the firmament. But we haven't had a comparable tool for seeing beneath terra firma - until now.

A first-of-its-kind transcontinental project called EarthScope, whose national office is located at OSU, is giving geologists an unprecedented look into the depths of North America. Their work is already turning up clues about silent quakes, creaking fault lines and the potential for a tremor to become a convulsion that topples buildings and sends tsunamis racing toward shore.

Just as astronomers are visualizing the heavens - from geysers on the moons of Saturn and Jupiter to the dance of planets around distant suns - EarthScope geoscientists from universities across the country are "looking" deep inside our own planet with thousands of precision instruments, some stationary, some transportable. The data from this multi-year collaboration will enable them to define the geological processes that shape the continent.

"This program is on the same scale for Earth scientists as Hubble is for space scientists," says Bob Lillie, OSU geosciences professor and education and outreach manager for EarthScope. (Read about Lillie's poetic approach.) "The difference is that our observatories are pointing downward into the Earth."

Casting the Net

Rather than capturing light through a lens, EarthScope observatories pick up fault movements and seismic waves through a sweeping array of seismometers, global positioning system (GPS) devices and other instruments. In 2004, scientists began deploying a network of 400 seismometers (known as the USArray) across the Western states. Added to that are nearly 1,000 permanent GPS instruments and borehole strainmeters in a West Coast EarthScope project known as the Plate Boundary Observatory. OSU is a member of the scientific consortia that manage these arrays.

Still another set of instruments takes stock of electromagnetic fields. Known as the USArray-MT, it is managed by Adam Schultz, OSU professor in the College of Oceanic and Atmospheric Sciences (COAS).

"The important thing about EarthScope is that we're monitoring in real time," Lillie says. "It's instantaneous. The GPS instruments take a reading every 30 seconds, and the seismometers record at even finer time intervals."

Telling the Story

While the National Science Foundation funds EarthScope, the program's national office at OSU coordinates scientific planning and communicates findings to an interested public (read EarthScope's onSite newsletter). "We have a lot of breadth and depth in EarthScope-type studies here," says Anne Tréhu, a professor of marine geology and geophysics in COAS. "Between the geosciences department and the marine geology and physics group in COAS, we have people working on a very broad spectrum of EarthScope-related problems."

At least 3 separate research projects at OSU and several more in the Northwest are funded by EarthScope competitive grants. "Several of these projects are related to earthquakes and the newly discovered phenomenon known as ‘episodic tremor and slip,'" says Tréhu. (Read about Trehu's research.) "OSU is the lead in one of these projects and a partner in others."

Data Are Accessible

In 2008, technicians began redeploying the USArray instruments eastward into the Southwest and the Rocky Mountain regions. (See an animation of a massive quake in China, picked up by the array in the western U.S.) By 2012, the 400 transportable seismometers will have migrated to the Atlantic Coast. Then they will be moved to Alaska. The facilities that maintain the data also make them accessible online for use by scientists, teachers, students and anyone else for research, education or planning.

And there's yet another first. In addition to one of the biggest coordinated captures of seismic and GPS data ever undertaken, EarthScope is monitoring movement and rising stress deep inside one of the world's most notorious faults: the San Andreas, infamous for devastating earthquakes up and down the California coast. A borehole, drilled two miles down to a depth where earthquakes originate, already is yielding exciting clues to the fault's geologic "personality" through minerals found in the rocks. Strainmeters have revealed faster-than-expected subterranean shifting.

EarthScope is a collaboration of NSF, the U.S. Geological Survey, NASA, the nonprofit research consortium UNAVCO, the Incorporated Research Institutions for Seismology and Stanford University. As the seismic instruments migrate eastward, the national office will move, too, rotating to a new university every four years.