Hi All. At present time Oregon appears to be pretty quiet place in regards to earthquakes. Major and great earthquakes don’t seem to happen there. That may not be the case. They do, but they have a longer time period between them. Don in creepy town

“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.”

“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 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.”

Marine geologist Hans Nelson (Texas A&M University's College of Geosciences) and paleoseismologist Chris Goldfinger (Oregon State University's College of Oceanic and Atmospheric Sciences) are building on the idea of Canadian scientist John Adams that shaking from Cascadia subduction zone earthquakes should generate sandy density currents. Such turbidity currents flow down deep-sea channels on the continental margin and deposit turbidite sand layers that record paleoseismic events.

"We are now coring into the deep-sea bottom of these channels to collect turbidite layer evidence of past seismic events," Nelson said. "Cascadia is an excellent area to develop this deep-sea paleoseismic record because 7,600 years ago, when Oregon's Mt. Mazama erupted, forming Crater Lake, 100 times more volcanic ash than that of Mt. St. Helens' 1980 eruption was deposited in the Columbia River drainage area."

"We have found that 12 turbidite bed layers occur for 600 km along the Cascadia margin, above the first bed with Mazama ash," Nelson said. "The best explanation is that great earthquakes on the subduction zone have triggered these events about every 600 years since the Mt. Mazama eruption 7600 years ago. Our deep-sea paleoseismic record now has verified the coastal record, extended it reliably back in time for thousands of years more and shown that the Pacific Northwest faces the hazard of future great earthquakes. "

http://www.4j.lane.edu/partners/eweb/ttr/quake/risk.html

http://www.scienceblog.com/community/older/2001/D/200114348.html

http://www.oregongeology.com/earthquakes/Coastal/OrGeoEqNTsu.htm

http://www.winfinity.com/cff/Info/tsu-inf-st.html

http://seattlepi.nwsource.com/connelly/joel02.shtml