Cascadian Subduction

October 9, 2006 1:53 PM

How likely/real is the threat of Cascadian Subduction (earthquakes, tsunamis and resulting volcanic activity)? Does it affect the lives, worries and insurance policies of Pacific North Western residents in places like Seattle and Portland?
posted by BrodieShadeTree to Science & Nature (19 answers total)

i work for an insurance rating company--we calculate risks for insurers, including earthquake risk. i haven't worked on the pacific northwest, but i did recently work on a project detailing earthquake risk around the new madrid fault in Missouri and Illinois. People there who wanted earthquake coverage were paying more dependant upon the proximity to the fault.
posted by lester's sock puppet at 2:11 PM on October 9, 2006

Portlands GIS data contains Earthquake Hazard information to a pretty detailed level. I would be astounded if this does not impact insurance.
link here - then pick 'Hazard - Earthquake' from the dropdown under the map.
posted by azlondon at 2:30 PM on October 9, 2006

It doesn't affect my life or worry me one bit.
posted by cmonkey at 2:50 PM on October 9, 2006

How real is it? Very real. How does it affect lives here? About none.
posted by Steven C. Den Beste at 2:59 PM on October 9, 2006

Anecdotally, it only affects me in one way, and that is I avoid using the Highway 99 Viaduct through Seattle whenever possible. This fragile edifice runs north-south with the waterfront to the west and downtown/sports stadiums to the east. When the big earthquake does hit, there will be many casualties along this stretch.
posted by vito90 at 3:06 PM on October 9, 2006

When I bought my house in Portland, I asked for earthquake insurance. Without missing a beat, the agent asked "And what part of California are you from?"

I think that the risk is quite real, although most people who live in Portland live in a state of comfortable denial. People in Seattle are more tuned in, thanks to the 6.8 that hit in 2001.
posted by ottereroticist at 3:18 PM on October 9, 2006

I think that the risk is quite real, although most people who live in Portland live in a state of comfortable denial.

That's a real shame. A little advance planning goes a long way toward ensuring survivabilty in a quake.
posted by buggzzee23 at 3:43 PM on October 9, 2006

Look, we (Seattle) had a quake that was larger (6.8) than one that flattened part of Iran a few months later. The best local news good get was some bricks that fell off a 50 year old chimney and some broken nicknacks.

Volcanoes are an ever-present threat but they won't come by surprise. St. Helens taught us that there will be a significant run-up to a major event.

Earthquakes will arrive without warning (even though the news-reciters will be shocked by that) but it will take a huge event to cause serious damage. Experts claim that will happen, someday, and they are probably right.
posted by trinity8-director at 3:51 PM on October 9, 2006

I grew up in Anchorage, Alaska. At least a couple times a year we'd have a sizable earthquake...no one would think twice about it. Conversations would usually go something like this:

"Did you feel that earthquake last night?"
"Yeah, damn thing woke me up."
"So, what're you up to this weekend?"

All in all it doesn't really adversely effect anyone's life. But yes, most people do have earthquake insurance.

Of note - Anchorage has very strict earthquake codes for new builds.
posted by ASM at 4:07 PM on October 9, 2006

That one "flattened part of Iran" due more to the poor construction methods used (mud-brick houses) than to the magnitude of the quake. If a 6.8 hit in NYC, you'd better believe there would be more damage than a few loose bricks.
posted by MikeKD at 4:09 PM on October 9, 2006

Response by poster: So, not a whole lot of "chicken little" syndrome going on up there?
I was on Vashon Island this last week and loved the area. But I am the sort of person who would let natural disasters, or threat there of, scare me off a move.
Are my fears unfounded?
posted by BrodieShadeTree at 4:11 PM on October 9, 2006

...due more to the poor construction methods used....

Which is the point I was attempting to make without, apparently, enough words to get it across. Earthquake-prone areas (in the US) have more stringent building codes so we don't end up like Iran, with everyone buried under mud bricks.
posted by trinity8-director at 4:21 PM on October 9, 2006

Are you talking about Pacific NW earthquakes in general, or only ones associated with the Cascadia subduction zone? Because here in Seattle, there are earthquake risks from 3 major sources:

-Subduction Zone earthquakes
-Shallow Crustal earthquakes
-Deep intraplate earthquakes

All three are taken into account when determining the earthquake risk for any particular location in the Puget Sound region.

I doubt these affect the worries of the average person in the PacNW when compared to people in Southern California or the SF Bay Area, simply because there have been no great casualties and massive property damage from earthquakes here.

But these risks very much affect the design and construction of every structure in the PacNW, from bridges and buildings, to pipelines and dams. Generally speaking, it makes these things more expensive to build. In that way, it ultimately affects all of our lives.

As far as insurance goes, most residential (homeowner's) policies will not cover earthquakes. If it is desired, it has to be bought as a separate policy. Those insurers will want to know exactly where your house is, when it was built, type of construction, etc in order to evaluate the risk. Not sure about commerical insurance.

trinity-8: that is not a fair comparison, as the Nisqually quake of 2001 was very deep, so the actual ground shaking was much less than if it had been a shallow 6.8 quake on the Seattle fault system (which would be a killer.).
posted by pitchblende at 4:26 PM on October 9, 2006

Are my fears unfounded?

Scientists say there will be a major earthquake ( > 7.0) along the Cascade range...someday. So, technically, no they aren't unfounded. While there is some variance in what they claim the end result will be, the bottom line is it will probably be pretty bad.

I've been through every quake in the past forty-(*cough*) years and can tell you this: you actually do get used to them. Most of 'em are little jigglers that have you wondering if it really was a quake.

All-in-all, I'll trade volcanoes and earthquakes to live here against pretty much any place in the country.
posted by trinity8-director at 4:34 PM on October 9, 2006

Following the "Spring Break Quake" of 1993 there was a lot of media in Portland about when the big one would hit. As a result, we've had a lot of bridge renovations that I suspect continue to this day, which certainly affects traffic. I also seem to recall a lot of problems with renovating city hall and the Portland Building. Portland State University has a lot of really visible renovations in the past year or so, especially in the student union. I think a lot of the renovation happens without fanfare and most people don't pay any mind.

There was an article in the Portland Tribune (?) about a year ago about how insufficient the Sellwood Bridge is. It scored 2 out of 100 on a federal sufficiency scale and city busses, large trucks and firetrucks are no longer allowed to cross it. One quote, that was treated kinda flippantly, in the article said something along the lines of, "the bridge is perfectly safe as long as there isn't an earthquake."

Likewise, there was a lot of media about the tsunami preparedness of the Oregon coast after the 2004 Indian Ocean tsunami and I suspect some public funds are building that infrastructure up right now. You certainly see a lot more tsunami warning signs on the coast today than I saw when I was a kid.

I'm neurotic, so, yeah, I worry from time to time. The old buildings in Seattle wig me out more than anything, though.
posted by Skwirl at 4:37 PM on October 9, 2006

I presume there's going to be a nasty earthquake while I'm living here near Seattle. I try to have the usual preparedness stuff that people anywhere should have: flashlights, bottled water, not letting the car get too low on gas, etc. Oh, and I'm trying to get my house retrofitted so it doesn't go sliding off the foundation.

The thought of an earthquake doesn't keep me up nights any more than the thought of terrorist attacks kept me up when I lived in NYC.
posted by The corpse in the library at 5:33 PM on October 9, 2006

I live slightly north on a river delta, slightly below sea level in many areas. (Richmond, BC, Canada)

It's a slight concern, but not one I think about much. My house insurance, including for the land we own which is not in this area, is about $36/month, so I'm not paying through the nose for this.
posted by Kickstart70 at 7:10 PM on October 9, 2006

Public radio has an occasional warning show about how to prepare and because my dad's an emphatic geologist, I followed through: water and food for three days in the house and some in each car (Powerbars are my food in this case), flashlights, pet food, and first aid supplies.

You can't get earthquake insurance on a brick house here in Seattle. We rent a brick house but we would not buy one.
posted by aimless at 7:18 PM on October 9, 2006

I seem to recall reading an article in Discover in Fall of 1999 about the lahar that could occur at any time from Mt. Rainier. I was in the San Juan Islands of WA at the time, coincidentally, and when I discussed the article with residents nobody really seemed to know about it, and if they did, they didn't care.
posted by nekton at 11:57 AM on October 10, 2006