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This rendition of an OSU tsunami shelter prototype shows a large multi-story building on stilts, likely to lessen the impac of the base of a tidal wave crashing through its vicinity.  (Source: Oregon State University)
Shake, rattle, roll and splash -- major seismic event could ravage the pacific northwest twice over.

There have been no shortage of powerful and often, sometimes catastrophically, deadly earthquakes in the past ten years. Sumatra, Haiti, Japan, Chile and more have suffered to various degrees from the results of plate tectonics and the roiling seas of magma far below the surface of the planet. Though, in the US, California has a reputation for being earthquake-friendly, it is a far cry from the only threatened west coast state.

Based on data collected from the Cascadia Subduction Zone, which lies off the west cost of North America and runs from northern California up to British Columbia, Oregon State University marine geologist Chris Goldfinger and team says the chance of a quake of high magnitude, 8 or better, is unsettlingly high in the next fifty years. Using telltale signs of seismic activity, they have mapped out a time line of major events for the last 10,000 years. As it turns out, the pacific northwest is about due for a major earthquake.

According to their findings, the Cascadia has already gone past the 75% mark as far as a major event within a generally rhythmic period of time. Over the past 10,000 years, they have found evidence of 41 large events, spaced at roughly 500 year intervals. Should no event occur in the next 50 years, the chances jump to 85%. There is no doubt, feels Goldfinger, that the event is coming -- it's just a matter of time.

At present, he states there is an approximately 37% chance that a magnitude 8 or greater quake will hit the southern section of the Cascadia Subduction Zone, which runs from northern California to near Newport, Oregon, in the next 50 years. Further north, the chance of an event is less -- 10% to 15% -- but with a better chance of being much stronger, magnitude 9 or greater.

Not all of the west coast is oblivious to this sleeping giant. Not only would a sizable off-shore event cause the standard stand-in-a-doorway building rumbling action, it would most certainly create a powerful tsunami in its wake. The last recorded high magnitude quake from the Cascadia was in 1700. Though no records exist from the Americas, Japanese historians recorded the ocean-traversing tsunami that reached their shore, crashing down at 30 or more feet in height.

The town of Cannon Beach, Oregon, is working with engineers from OSU to create an earthquake and tsunami shelter for its residents using advanced construction techniques and an eye for vertical space to stand above the wave. If completed, it may be the first tsunami shelter built outside of Japan.

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RE: Bias? Fishiness?
By StevoLincolnite on 5/25/2010 12:08:39 PM , Rating: 2
There's also this idea that the longer we go, the worse it will be.

That's because Earthquakes caused by tectonic stress DOES get worst the longer we go without one, as the stress increases and increases over time leading to a larger Quake.

RE: Bias? Fishiness?
By DesertCat on 5/25/2010 12:45:39 PM , Rating: 2
That's very much the case. We have some understanding of the mechanism that leads to earthquakes in the area. While we look at recurrence intervals for earthquakes to help in prediction, this is not simply a random phenomenon. Pressure is building where the Juan de Fuca Plate is locked with the North American Plate and the elastic limit of the rock will be reached sooner or later.

What Goldfinger and his colleagues have done is help show that Cascadia operates in sections instead of as a continuous feature. At one time there were fears that this fault zone would unzip from southern Oregon all the way to B.C. Canada. Now it appears that it behaves in a more segmented fashion. By understanding which sections are at the most risk, authorities can better concentrate preparedness and engineering resources to those areas first.

In the big picture, it has only been within the last ~20 years that Oregon and Washington have come to understand the potential for a 8+ magnitude earthquake. Oregon has started the process of retrofitting public buildings so that they do not collapse during a large quake, but that takes time and money (much less if the building is designed that way from the start). The schedule for all of Oregon's public schools to be finished with eq retro-fitting? The year 2032. Since it now appears that the southern section has a greater probability of having an earthquake in the short term, one would hope that funding would be concentrated there first.

Oh, and the vertical evacuation idea for tsunamis is being pursued in many seaside towns where no high ground (50+ feet above sea level) is nearby. Given the proximity of the Cascadia fault to the shoreline, residents have about 25 minutes from the time of the earthquake until the first tsunami wave hits. As a result, other options need to be considered. If I remember right the structure in question is the town hall, which will serve as something of a life raft in the case of a tsunami event.

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