Half Of Oregon's Critical Bridges May Collapse In Magnitude 8 or Greater Quake

[Dougtone]

How many Oregon bridges will hold up in a major earthquake?

New data compiled by the Oregon Department of Transportation reveals at least part of the answer. The results aren't pretty for a region facing 1-in-3 odds of a magnitude 8 or larger earthquake in the next 50 years.

Read the entire article at...
http://www.opb.org/news/series/unprepared/earthquake-oregon-bridges-collapse/

[nexus73]

The area I live in will be sliced into islands by downed bridges, a busted earthen dam and landslides.  Our one saving grace is the North Spit to absorb the tsunami's impact.  Cities closer to the ocean will wind up resembling Hiroshima, scoured clean.   

101 to the Coast Range is the worst of it.  Coast Range to Cascades has major damage.  Cascades to past US 97 and the edges of the Great Plateau receive minor damage.  The quake hits everything from southern British Columbia/Vancouver Island to Mendocino County CA hard.  Damage will be seen as far south as Sacramento and San Francisco.  Power outages will plunge the West other than SoCal and Baja California into darkness. 

Since Oregon and Washington don't have the same building standards as Japan and California, look for even more destroyed structures than those areas have when quakes come calling.

For possible good news there's this: Two days prior to the 2011 Japan quake there was a 5.0 offshore.  Maybe we get that kind of shot across the bow before we're sunk.  30 seconds before the Big One hits there will be rumbling and the animals will go crazy.  Move fast!

Rescue efforts figure on dealing with the light damage areas in 24 hours.  The I-5 corridor should receive aid in 48 hours.  Coastal areas hope for resupply in a week and evacuation in a month. 

Since there has been a large increase in quakes along the Cascades and offshore over the last decade, I expect the subduction zone to break loose within the next 10 years.  Scientists hate to panic people, thus the half-century time frame.  We are already overdue at 315 years since the last one.  In terms of geological time the next tick of the clock sees the whole thing go boom.  That's kinda-sorta like dog years in reverse...LOL!

Don't count on the government.  During Katrina only 10% of the emergency responders responded out of the gate.  Remember "Good job Brownie"?  If you want a helping hand you had better look in the mirror first, then see if you can work with people within walking distance since you are not going to be driving anywhere.  Stock up now, assume the worst will happen and hope for the best!

Rick

[Sub-Urbanite]

The area I live in will be sliced into islands by downed bridges, a busted earthen dam and landslides.  Our one saving grace is the North Spit to absorb the tsunami's impact.  Cities closer to the ocean will wind up resembling Hiroshima, scoured clean.   

Have you seen the new DOGAMI maps? Looks like downtown Coos Bay is toast even in the event of the mildest events.

Since there has been a large increase in quakes along the Cascades and offshore over the last decade, I expect the subduction zone to break loose within the next 10 years.  Scientists hate to panic people, thus the half-century time frame.  We are already overdue at 315 years since the last one.  In terms of geological time the next tick of the clock sees the whole thing go boom.  That's kinda-sorta like dog years in reverse...LOL!

Sorta. If you look at the historical record, there are often some pretty big gaps between quakes. And a subduction quake on the south end of the fault (but not along the entire fault) would still cause the tsunami but likely not result in the catastrophic shaking further north.

[mcarling]

Not all the "vulnerable" bridges would fail catastrophically -- even in a magnitude 9 earthquake.  Some would suffer minor damage and probably some would be unscathed.

Also, some bridges are being replaced such as the Sellwood Bridge over the Willamette (a county bridge for which ODOT is not responsible).  Sooner or later, the Interstate Bridge over the Columbia will be replaced (also a bridge for which ODOT is not responsible).  The point is that bridges do wear out and get replaced.  It's likely that many bridges will have been replaced before a major earthquake will strike Oregon.

Replacing bridges that have insufficient capacity (such as the Interstate Bridge) or which have worn out (such as the Sellwood Bridge) with modern seismic-robust designs makes more sense than replacing bridges just based on theoretical seismic vulnerability.

[nexus73]

Well folks, it looks even worse the more you find out.  Want some proof?  Here ya' go!

http://www.opb.org/television/programs/ofg/episodes/2701/

When PBS does a documentary and does it as well as this one, you'll be rightfully made aware I guarantee it! 

1000 bridges or so are expected to fail in Oregon alone.

Rick

[mcarling]

I watched the documentary posted by nexus73.  Like most documentaries, it gives a one-sided view.  The only person they interviewed with a contrary view was the town manager they tried to vilify.

Anyway, if one accepts the conclusion of the documentary that Oregon should prepare for a 9.0 Cascadia subduction earthquake and that Redmond will be the center of relief efforts, then Redmond should be better connected to the rest of the country.  Perhaps the 2x2 section of US97 should be extended south from Sunriver to Klamath Falls and north from Redmond to I-84.

[nexus73]

One-sided?  Well friend, either you ARE or you ARE NOT prepared.  That is so binary as to make it an easy choice...LOL!

Rick

[mcarling]

Preparedness of infrastructure is not perfectly continuous, but it's so granular as to be virtually continuous.  It's almost as far from binary as it could be.  If it were binary, then there would be one very specific set of (thousands of) very specific needed projects, which all completed would represent preparedness but if even one were not completed or completed to a lower standard would represent unpreparedness.  That would be binary.  The reality is quite different.  For example, would rebuilding US97 through Oregon to interstate standards be a necessary part of preparedness for a 9.0 Cascadia subduction quake?  I think there is room for different opinions on that.  Certainly it would improve preparedness.

The right way to think about these problems is to calculate for each possible project an estimate of the cost of saving a statistical life.  Then order the list and start with the projects that save the most lives for the least money.  One can find such lists for various kinds of efforts, from restricting smoking to improving infrastructure to recycling to cancer research.

I would support raising the standard for new bridges from no immediate loss of life during an earthquake to requiring that the bridge be useable after the earthquake.  This point is explained well in the documentary posted by nexus73.

[mcarling]

Here is an OSU press release about the revised estimates of a Cascadia subduction earthquake, nearer to the original academic research and less imbued with hyperbole than the tabloid sensationalism from OPB: http://web.archive.org/web/20100527090117/http://oregonstate.edu/ua/ncs/node/13426