I recently did a seismic retrofit of my 1920s house. Note that the house had NO connection from the foundation to the sill plate, nor from the sill plate to the stringers. I imagine that to be the case for all pre-1940s houses in Portland. Yikes.

In a Big One, the foundation that you just strapped the house to will crumble like a cookie. But now it looks good, and with it you can get earthquake insurance... with obscene premiums... and huge deductibles... at least for this year.

Correct me if I am wrong, but my understanding is that the major fault lines are a few dozen miles off the coast (like the Chilean earthquake). While Portland will be hit hard, earthquake damages diminishes exponentially from the epicenter... at least that's my understanding.

This site has some good maps of the relative risks of earthquakes for various parts of Portland.

http://nwdata.geol.pdx.edu/DOGAMI/IMS-16/

(Summary: West hills has highest risk.)

This one in particular is informative...

http://nwdata.geol.pdx.edu/DOGAMI/IMS-16/Maps/Images/m90_pga.jpg

This shows the impact to Portland for a 9.0 (!) earthquake from the Cascade subduction zone (the big one)... damage to Portland is modest.

It is true that the intensity declines the further away you are and the subduction zone is offshore. The problem, however, is that subduction zone earthquakes can last for a minute or longer and much of this area is on soil that would liquefy. That is particularly a problem for downtown Beaverton area (also why they cannot build tall buildings there). If you survive that then you have the bigger problem of fires. Neighborhoods like NW Portland & much of the east side, full of old wooden houses and natural gas mains, would be sitting ducks. Fire departments wont be able to respond.

damage to Portland is modest.

Don't stop... believin'...

I saw a film that claims the length of time for an earthquake is the time it takes the fault to rip, and our fault (even though it isn't really our fault if you know what I'm sayin') is a big one - 600 miles long - so our 9.0 earthquake will last 5 minutes.
The scientist stressed that nobody really knows how long our skyscrapers can take a quake like that as the last one here was in January of 1700.

Speaking of quakes, Rebecca Solnit wrote a very good book called "Paradise Made in Hell" about the after-casualty casualty. Her research shows that, in the immediate aftermath of a big disaster (quake, fire, etc.), people respond admirably, with mutual aid and compassion. Typically, trouble starts as soon as government begins to reorganize, as it immediately channels the fears of the wealthy that "The Mob" will go crazy and start acting like humans with rights; thus, police and national guard troops start repressing people and then things go bad in a hurry.

We saw in Katrina that people, left to themselves, were pretty creative and helpful. But once the feds really got going, shooting people and taking away their weapons became a much bigger priority than providing them with food or shelter -- even though there's no emergency exemption to the 2d Amendment. Turns out, the same is true throughout history -- the disasters are events, but the real damage starts when people like Fireman Randy start taking charge.

It's a great book and, I think, good food for thought about how to prepare for the 9.0 that's coming.

There's another theory kicking around that involves the planet as one system. In other words, a big quake far away from where you are, makes the next one more likely to be near you.
I'm not saying I believe it, but notice how the Aleutian Islands quake came right on the heels of this?

I lived in Christchurch for half of a year while I was studying abroad at the University of Canterbury there a few years back. It's an absolutely great town, on the ocean along it's eastern side, 1 hour's drive from the mountains to the west, and on the south bordered by a beautiful hilly peninsula formed by an extinct volcano with dozens of little inlets and bays. Plus a idyllic "river" (a stream by US standards) that meanders through the city, a huge park/botanical gardens right next to downtown, and a pretty moderate climate. Oregonians would find a lot there that reminds them of home. Plus New Zealanders are some of the friendliest people I've ever met, and with a great sense of humor.

It's shocking to see the pictures of streets downtown lined with rubble and with buildings whose facades have been destroyed standing open for everyone to see inside. It's relieving to hear that there were no deaths and only 2 serious injuries caused by the quake.

Nick, here's today's update on the 7.1 in Christchurch:
http://news.yahoo.com/s/ap/20100905/ap_on_re_as/as_new_zealand_earthquake

"'Thank God for earthquake strengthening 10 years ago,' the Anglican dean of Christchurch, the Rev. Peter Beck, told TV One News on Sunday."

Perhaps Portland should place its request for "earthquake strengthening" now. But will Rev Peter Beck's God hear Portland above the pleadings of so many others?