Pacific Northwest At Risk For Mega-Earthquake 457
Hugh Pickens writes "Science Daily Headlines reports on research by Oregon State University marine geologist Chris Goldfinger showing that earthquakes of magnitude 8.2 (or higher) have occurred 41 times during the past 10,000 years in the Pacific Northwest. By extrapolation, there is a 37% chance of another major earthquake in the area in the next 50 years that could exceed the power of recent seismic events in Chile and Haiti. If a magnitude-9 quake does strike the Cascadia Subduction Zone, extending from northern Vancouver Island to northern California, the ground could shake for several minutes, highways could be torn to pieces, bridges might collapse, and buildings would be damaged or even crumble. If the epicenter is just offshore, coastal residents could have as little as 15 minutes of warning before a tsunami could strike. 'It is not a question of if a major earthquake will strike,' says Goldfinger, 'it is a matter of when. And the "when" is looking like it may not be that far in the future.'" Read below for more.
The last major earthquake to hit the Cascadia Subduction Zone was in January 1700. Scientists are aware of the impact because of written records from Japan documenting the damage caused by the ensuing tsunami, which crested across the Pacific at about 5 meters (15 feet). Knowledge about what happened in Oregon and Washington is more speculative, but the consensus — gleaned from studies of coastal estuaries, land formations, and river channels — is that the physical alteration to the coast was stunning. The outer coastal regions subsided and drowned coastal marshlands and forests, which were subsequently covered with younger sediments. "Perhaps more striking than the probability numbers is that we ... have already gone longer without an earthquake than 75% of the known times between earthquakes in the last 10,000 years," says Goldfinger. "And 50 years from now, that number will rise to 85 percent."
Re:No, Mr Bond, I expect you to die... (Score:5, Informative)
Well, at least it's better than the whole laser-beam-to-the-crotch method of execution.
What? Of course I'd rather be drowned, crushed, and torn apart by massive hydraulic forces!
Yeah! Yeah! I AM a guy! So what?
Re:Yet another reason... (Score:4, Informative)
Re:Yet another reason... (Score:4, Informative)
Re:Yet another reason... (Score:2, Informative)
FYI: California isn't in the Pacific Northwest.
Pacific NorthWest? (Score:4, Informative)
For the rest of the world they are referring to the North Eastern Pacific.
Re:Yet another reason... (Score:3, Informative)
... why I'm glad I don't live in California.
Here's a list of the earthquakes for the last 7 days [usgs.gov]. California is not the only place to be concerned about.
Re:damned lies (Score:4, Informative)
No statistician I have met was ever willing to extrapolate beyond the set.
How many have you met?
I ask because it is done every day. Virtually the entire work of theoretical econometrics is extrapolation, and complicated by the absence of the usual experimental controls. Climate scientists do it as well. Obviously the results are subject to a lot of debate. Some bookies have statisticians on staff. Insurance companies want all sorts of extrapolation from their actuaries. Players in futures markets aren't doing seat of the pants guessing. U Iowa has been studying prediction markets of many kinds on a large scale for a very long time, and have well developed statistical models. Large companies and governments alike pay people to forecast everything from crime rates to how many drilling permits to hand out.
Re:Well, as long as we're talking catastrophe (Score:5, Informative)
Somehow I doubt it. Vulcanism is a completely different natural process than plate tectonics. If anything, a massive earthquake like this, even if its energy did reach that far away, would, at most, shift the location of the hotspot where the future eruption is likely to take place. Which means that a section of thin earth (the hotspot) would be pushed away and replaced with a section of thicker earth that hadn't been warmed to the same degree yet. This should minimize the chance for a new eruption, not increase it.
Re:damned lies (Score:4, Informative)
Re:And... (Score:4, Informative)
Governments in the area have been reacting to this news for a couple decades. In BC, we're spending over a billion dollars seismically upgrading critical bridges and making sure the older schools and hospitals don't colapse on their occupants. They've begun emergency preparedness drills, etc.
The problem is: at 8+ magintude, all plans go to crap...
Re:Well, as long as we're talking catastrophe (Score:3, Informative)
I actually prefer the variant "vulcanism" because it shows the roots of the word going back to the god Vulcan. "Volcanism" just doesn't seem as poetic to me.
We are actually aware of this up here... (Score:3, Informative)
More interesting than when the big one is going to hit is how well we are setup to handle it when it does. I was in a building rated only for a 7.0 Ricter magnitude quake during our last major quake (which measured 6.8), and there were major fears that the building was going to collapse either during or just after the quake. Luckily for me, it weathered the quake with only minor damage.
However, after the Chile quake last year, I heard a report from our local NPR affiliate comparing the infrastructure of the NW with the infrastructure of Chile (our buildings are built to roughly the same standards, and are around the same age), and mentioning that the state governments up here were taking interest in learning from the lessons of that quake to prepare better for our next big quake.
Re:And... (Score:5, Informative)
Actually, no. Vancouver is located near a triple-plate junction, and is susceptible to deep magnitude 9 subduction quakes with minimal surface shaking (akin to Chile), or shallower magnitude 7s with a lot of surface shaking. Locally, a magnitude 7 is a lot more problematic, although a magnitude 9 would put everyone else on the rim on tsunami-watch.
Richmond and the unconsolidated saturated sediments they live on below sea water behind a dyke is pretty much out of luck in prolonged shaking, as the liquefaction means they'll discover they built on oatmeal. The only way to earthquake-proof that is to keep Richmond entirely agricultural.
But for the city proper, it's pretty much set. Vancouver is built on glacier-compressed sediment, and once you've had 2km of ice squishing everything flat, as far as earthquakes are concerned, it's pretty much bedrock. The engineered fill around False Creek/Granville Island/the downtown docks are likely to have more problems (honestly, I'm concerned about those nice, huge cranes toppling under a bit of liquefaction, exactly like waterfront in Haiti), but as far as "places with people" go, the biggest danger should be the shower of broken glass in the city core. Even personal preparedness is fairly high: approximately 2,000 students per year pass the intro to disasters course at UBC; I don't have the numbers but I'd guess at least a few hundred take the equivalent course at SFU.
Vancouver Island protects the mainland from tsunami; the only real tsunami-danger east of the island is locally in the fjords if the earthquake triggers a landslide (likely things will fail; not so likely anything big enough will go in any one place to really cause a threatening seche). As for the west coast of the island, this past year's Chile-warning was a good practice run. The last-mile notification is still bumpy, but getting better.
Victoria (on the south tip of Vancouver Island) worries me more -- the current subduction has buckled the island up by approximately 15m, which is an awful lot to deal with if it all slips at once. This is made more complicated by the large proportion of the elderly (Victoria is a major retirement destination in Canada), who have lowered resiliency in emergencies.
Re:Central tendancy (Score:4, Informative)
It's unknown if large geological events like this occur according to any central tendency. It may be that the mean time between large earthquakes is not related to the mean. Ultimately we have no idea, the data is not good enough to say...
This is an absurd contention. Paleoseismic research provides precisely this information, and is a very well developed field. Further, we actually understand the basic mechanism that creates very large earthquakes and thus have a normative theory that explains and reinforces a purely statistical approach. Large earthquakes follow the same frequency law (the Guttenburg-Richter Law) as small and moderate earthquakes.
It strikes me as sad (but I guess not surprising given the anti-scientific political culture on the right) to find this same contra-factual "we don't really know anything" claim for earthquake geology that is currently pushed by those hostile to climate research.
For a useful backgrounder on earthquake statistics loook at: www.earthquake.ethz.ch/education/NDK/NDK
Re:No, Mr Bond, I expect you to die... (Score:3, Informative)
It's also has the highest number of microbreweries of any city in the world.
Re:Yet another reason... (Score:3, Informative)
IRIS [iris.edu] maps them out for you.
Re:Pacific NorthWest? (Score:2, Informative)
i guess only Americans would understand that...
For the rest of the world they are referring to the North Eastern Pacific.
I'm Canadian you insensitive clod! It's the Pacific Southwest.
Re:And... (Score:2, Informative)
A few factual corrections, although I agree with the tone.
The earthquake building code for the United States is the same throughout the country, but it zones the country by expected earthquake risk. California is in a high-risk zone, but so are several other locations in the country. BC, California, and Japan all have fairly comparable building codes. So yes, California's code is very, very good. But it's not, technically speaking, "the best."
Next, California has relatively small translational earthquakes caused by the plates rubbing past each other. This leads to intensely focused, fairly shallow earthquakes, similar to that experienced by Haiti. It's common for one city to be hit hard (LA during the Northridge Quake, SF in '89...) and the surrounding region to be pretty much unaffected.
The Pacific North West and Chile have subduction earthquakes, also called megaquakes because of their incredible magnitudes. These earthquakes are caused by one plate subducting under another, and lead to deep earthquakes with less-intense shaking felt over a larger area. They are also commonly associated with tsunami-generation because of underwater vertical displacement (Sumatra was another subduction quake).
Geologically, the regions you're comparing have very different causes for earthquakes, very different types of shaking felt at the surface, and different impacts on the rest of the rest of the world.
Re:Well, as long as we're talking catastrophe (Score:2, Informative)
The Yellowstone Caldera is not related to the subduction melt. Mount Saint Helens, Mount Rainier, and the rest of that volcanic chain are related, but plates shifting about in an earthquake doesn't increase or decrease rates of melting.
A bit off topic, but a fun bit of trivia: oceanic plates produce non-violent volcanoes (like Hawaii), continental plates produce highly violent volcanoes (like Yellowstone, although most are very very very small), and ocean melt passing through continental plate produce intermediate volcanoes (like Mount Saint Helens) which are technically less violent than purely andesitic volcanoes, but have larger volumes of magma so are the most destructive. (For the chemistry nerds, it has to do with percent-silica & trapped gas).