Hi Bob. I think this can also be added to what you were told. Take Care…Don in creepy town.

MAY 1999:

SEATTLE -- New research indicates that a massive earthquake could occur directly underneath the Oregon Coast Range and the western portion of the Willamette Valley. For nearly 15 years, scientists have warned that a magnitude 8 or 9 earthquake could strike about 30 miles offshore and rock the coast, causing severe shaking and huge tsunamis. However, recent data gathered from satellites by scientists at Oregon State University and three other institutions show that the colossal quake could hit much farther inland and cause more severe damage to a larger area -- including the more populated cities of the Willamette Valley such as Portland, Salem and Eugene.

No one knows when such an earthquake might strike the Northwest, but the geologic evidence suggests that such quakes occur about every 400 years, plus or minus 200 years.The last major earthquake on the Oregon coast -- believed to be a magnitude 9 -- occurred 300 years ago, previous studies showed.

The research team found that the locked portion of the Cascadia Subduction Zone -- where the eastward-moving Juan de Fuca Plate plunges under the western-moving North American Plate -- extends beneath the Coast Range and as far as the western side of the Willamette Valley. The locked zone probably is wider than previously thought, although the new data give less information about the width.

The researchers expected to find little movement because of the lack of earthquakes and previous data that showed little uplift in central-western Oregon, something commonly associated with a locked subduction fault. Instead, they found that the ground is moving nearly half an inch a year toward the northeast. The rapid velocity worries earthquake researchers and indicates that the underlying plates are locking up rather than sliding by each other, resulting in incredible strain.

As the Juan de Fuca Plate presses forward to the northeast in the locked zone, it causes the piggybacking North American Plate to bulge upward and inland toward the northeast. The pressure continues to build for years until an earthquake unleashes the stress in one powerful jerk, causing the bulge to collapse and forcing the area to drop instantly.

"We were very surprised by the results we got," said Goldfinger, an OSU assistant professor of oceanography. "It was quite different from what we expected. We thought this would be an area that would show little, if any, movement." The half-inch of movement each year is imperceptible, but the accumulated pressure that has been stored since the last major earthquake in 1700 can only be unleashed in an earthquake.

"That means there's been 300 years of strain that will be released," said John L. Nabelek, a seismologist and OSU associate professor of oceanography who participated in the study. "And it's just not the proximity of the strain to larger cities that is a concern, but we've found that the surface area of the entire locked zone is much larger than previously thought. That means a larger quake."

Goldfinger said the data suggest that the two plates are "essentially bolted together -- they're 100 percent coupled.

"In addition, the Coast Range is an extremely strong, rigid block of rock that is more than capable of accumulating the sort of energy you need for a large earthquake."

The new findings have made Goldfinger, who in previous years argued that the largest subduction-zone quake was more likely to be a magnitude 8 than a 9, rethink his theory. "This changes my views 180 degrees," he said. "The whole argument for an 8 rather than a 9 disappears." Although quakes of either size would be devastating, shaking from a magnitude 9 event would last two to three minutes -- about twice as long as the shaking a magnitude 8 quake would produce.

Researchers elsewhere in the Northwest have come up with similar results using the satellite-based Global Positioning System. The locked zone between the plates extends farther landward beneath Washington and Southern Oregon as well, and a little farther under Vancouver Island than previously thought. A larger research effort, planned next year, will examine an area from Northern California to Canada, including Portland.

The Cascadia Subduction Zone is a 750-mile long fault that runs 60 to 150 miles offshore from British Columbia to Northern California. Similar subduction zones have produced the two largest recorded earthquakes in the world -- a magnitude 9.5 quake on the coast of Chile in 1960 and a magnitude 9.2 quake in southern Alaska in 1964.
No quakes of that size have been measured in Oregon's brief recorded history, but evidence from buried marshes along the coast indicate that such events occurred at least seven times in the past 3,000 years. The last one hit the coast in January 1700, and large quakes appear to have struck about 1,100 years ago, 1,300 years ago and 1,700 years ago.

Curt D. Peterson, a professor of geology at Portland State University who has uncovered many of the buried marshes along the Northwest coast, said the new research supported his decade-old theory that the locked zone might be twice as wide as thought and capable of generating a huge quake.

"I hope this new evidence is going to help planners and government agencies get back on track about the seriousness of the hazard. The metro areas such as Seattle and Portland need to examine what a magnitude 9 means in terms of the whole region going all at once," Peterson said.

Mark Darienzo, earthquake and tsunami program coordinator for the Oregon Office of Emergency Management, said the study supported concerns that a huge subduction-zone earthquake "is not just a coastal problem, but could be an inland problem as well."

"More research is needed," Darienzo said, "but these new findings show that the potential for such a quake can't be overlooked -- it shouldn't be just tossed aside."

• Oregon Subduction Quakes