The Northwest has discovered damage from an earthquake that happened over 3 months ago, on February 28?as well as one that occurred 12,000 years ago.
The recent 6.8 magnitude quake in Washington state was strong enough to crack the Capitol dome near Olympia. The entire city of Seattle slid about 5 millimeters northeast and Olympia dropped a quarter of an inch. But no homes or businesses were leveled, so area residents thought they had missed the worst effects.
Now thousands have discovered that it was an invisible disaster?that they have earthquake damage after all. Their foundations are cracking, chimneys crumbling, walls buckling. 30,000 people have reported damage to their homes. ?FEMA is getting 200 to 300 damage calls per day. The magnitude of this keeps going,? says Rob Harper of Washington Emergency Management. ?Initially people had no problem but now they?re finding more damage.?
Harper told of one person whose home had a cracked foundation that cost $50,000 to repair. The entire front end of the house had to be shored up and the family had to move out. Neil Molenaar, a Church World Service disaster response facilitator, says, ?One elderly lady told us her house feels like a chair when the train goes by.? He adds, ?We?re working an invisible disaster? because they can?t drive down the street and tell which homes have been affected.
Marcy DeVries, a disaster volunteer, says, ?The biggest difference is that, ordinarily, a disaster is in one or at least a somewhat defined area, like a certain stretch of blocks or along a riverbank. But this is all over. That makes assessing damages very difficult. Usually we can go from house to house?in this case it?s many miles.?
Geologists believe another quake of an unknown magnitude could occur at any time, because Washington sits on top of many faults. ?The Puget Sound area is associated with an earthquake hazard similar to that of Chile, Alaska or Japan, where the world?s largest earthquakes occur?I think this earthquake created more awareness of all the unstable earth we live on,? says Harper.
In Portland, evidence has been discovered that a major earthquake hit the downtown area about 12,000 years ago along a fault that is now considered to be an active threat. Geologists have long known about the Portland Hills fault that runs beneath the city, but they did not know how big a risk it was. John Beaulieu, the chief state geologist, says, ?It?s a risk we simply can?t afford to ignore.?
Surface evidence of the quake was discovered by state geologist Ian Madin, who noticed distortions in sediment exposed by workers digging a trench at a suburban Portland school. Further study of the sediment indicated that a quake occurred about 12,000 years ago, at the end of the last Ice Age. That may seem like a long time ago, but to geologists like Madin it?s ?almost yesterday.?
The fault zone that triggered the quake is several thousand feet wide and passes directly through the heart of downtown Portland, stretching for 30 to 50 miles. Beaulieu says the Portland fault has the potential for an earthquake similar to the 1994 quake in the Northridge section of Los Angeles that measured 6.7, did more than $15 billion in damages and killed 72 people, or the recent quake in Washington.
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