CORVALLIS, Ore. -- Scientists at Oregon State University said a new analysis of a 200-mile-long fault line off the Oregon coast shows it is more active than the San Andreas Fault in California.

They said the Blanco Transform Fault Zone likely won't produce the catastrophic earthquake many predict for the Pacific Northwest. But they said an earthquake of magnitude 6.5 to 7.0, capable of inflicting heavy damage, is possible, if not probable.

The Blanco fault begins about 100 miles away from Brandon and extends to a point about 300 miles off the coast of Newport.

During the past 40 years, there have been about 1,500 earthquakes of magnitude 4.0 or greater along the Blanco Transform Fault Zone, and many thousands of smaller quakes.

The Blanco fault is the boundary between the Juan de Fuca and the Pacific plates.

The proximity to the Oregon coastline makes it possible for land-based seismographs to measure the ocean earthquakes. Bob Dziak, a marine geologist at OSU, also monitors undersea seismic activity using a hydrophone system.

Dziak said there was a swarm of 600 earthquakes in 10 days in the region in April. Those quakes reached 5.4 and 5.0 in magnitude.

While the quakes have been high in magnitude, OSU researcher Jochen Braunmiller said the chances of a major tsunami are slim because the plates move sideways past each other.

"You need quite a bit of vertical displacement on the ocean floor to generate a tsunami," Braunmiller said. "And earthquakes along the Blanco fault don't generate it."

Results of the OSU study appear in the Journal of Geophysical Research.

Related:

April 22, 2008: More Quakes Rumble Off Oregon Coast

Nov. 19, 2007: 5.8 Earthquake Reported Off Ore. Coast

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