The Science Of The Cascadia Fault Earthquakes

February 1, 2013 6:56 AM

Those who may have seen articles such as this Discover Magazine article, may want to know more about the Cascadia fault and the possibility of a Fukushima type earthquake [previously: here]. Here is the best summary of the science that led to the discovery of the 1700 earthquake and the history of earlier quakes. Of particular interest is a beautiful piece of data display in Figure 9 that shows the spacing in time and extent of earthquakes over the last 10,000 years based on evidence of tsunamis produced by the quakes. Finally, here is a great pieces on Surviving a Tsunami should the need arise.
posted by BillW (17 comments total)

I suspect Mr. Tufte might take issue with your description of that graphic, Bill. Can you provide some interpretive guidance to make it readable? I couldn't make head or tail of it.
posted by mwhybark at 7:34 AM on February 1 [5 favorites]

As far as I can tell, the y axis is years prior to 1950(?) while the x axis is latitude along the coast. The different little markers indicate tsunami evidence from each of those locations along the coast (with some error). The green dashed lines and their lighter green backgrounds show tsunami dates and and confidence levels. These are labeled as T1 through T18 on the side. So I guess the next one to occur gets to be tsunami zero (also an under-appreciated skidcore band from the 80s)?

Basically it support the idea that tsunamis happen every couple of hundred to a thousand years with a few smaller slips in between only showing up in southern Oregon.
posted by andorphin at 7:56 AM on February 1 [1 favorite]

andorphin is exactly right. Would have been nice if the marine data vs. the land data had distinct color codes, but I guess they ran out of symbols. Oh, and above the top of the graph are the names of locations on the coast that move (as andorphin suggested) from north to south as you go left to right. That's why the bigger quakes are wider: they suggest a fault break/tsunami that extends farther up the coast.

Hmm. Tsunami Zero reminds me of the William Gibson novel Count Zero which riffed on the computer instruction count zero interrupt. That seems vaguely spooky...nice one andorphin!
posted by BillW at 8:30 AM on February 1

Basically it supports the idea that our treasured green lines are under attack on all sides by tribes of little pill-shaped creatures, some of whom have pointy sticks.
posted by oulipian at 8:31 AM on February 1 [2 favorites]

ooohhhhh earthquake porn. thank you (so much for all the work I need to get done today...)
posted by supermedusa at 9:04 AM on February 1

and although I assume all Mefites have already read Peter Watt's incredible Starfish trilogy, if you haven't and you are interested in this topic, you really need to!
posted by supermedusa at 9:06 AM on February 1

just finished the first article. daaaaaaaaaaamn that is scary (and really fascinating!! now I'm wishing I'd followed an alternate life/career path to work in USGS studying this stuff!! its sooooo cool omg!)
posted by supermedusa at 9:53 AM on February 1

Living in Portland I'm always looking around at stuff and going, "Yup, that'd get wiped out. And that. That, too." I get to feeling like Eeyore.
posted by Chutzler at 10:47 AM on February 1 [3 favorites]

I wish I could find an article I read in recent years, that speculated in gruesome but fascinating detail what the effects of a large earthquake and tsunami would be on the northern Oregon and southern Washington coasts and inland. In it I recall the author saying that a tsunami would of course devastate the coastline, but wouldn't affect Portland all that much as the wave would dissipate long before it crept up the Columbia. However, the earthquake itself would do plenty of damage to buildings and infrastructure; also the soft landfill along the banks of the Willamette would liquefy, bringing down all those nice shiny towers built on the waterfront at the southern end of downtown.
posted by Greg_Ace at 11:38 AM on February 1

also the soft landfill along the banks of the Willamette would liquefy, bringing down all those nice shiny towers built on the waterfront at the southern end of downtown.

If those towers don't have foundations that go down to the underlying bedrock, the architects that designed them and the people who financed them should be half-hanged, drawn and quartered.
posted by b1tr0t at 12:16 PM on February 1 [1 favorite]

supermedusa, you think this is interesting stuff, try this Wikipedia entry on the Farallon Plate. That will blow your mind, particularly the NASA model of what happened as it plowed into the mantle.

I grew up surrounded by geophysicists and I still managed to be captured by the glamour of computers! ;-)
posted by BillW at 12:18 PM on February 1

thanks BillW! I dont know anything about the Farallon Plate, but will soon remedy that!

"glamour of computers" I lol to keep from crying ;)
posted by supermedusa at 12:20 PM on February 1

the Farallon Plate article is fascinating!
posted by supermedusa at 12:30 PM on February 1

mwhybark and oulipian, I see your points, but what makes it so exciting is that it summarizes 20 years of studies into one chart that describes the who, what, when where and the why of Pacific Northwest earthquakes. It even gives us some clues as to when the "murderer" will strike again. Not all data graphs have to be intuitively obvious to people unaware of the domain.
posted by BillW at 12:31 PM on February 1

I wish I could find an article I read in recent years, that speculated in gruesome but fascinating detail what the effects of a large earthquake and tsunami would be on the northern Oregon and southern Washington coasts and inland.

Greg_Ace, here are some links that look at what-ifs for Puget Sound, which presumably would be less affected by an oceanic tsunami, followed by one looking at a Cascadian quake and tsunami. I don't think the Cascadian material is what you describe exactly but the event visualized is similar.

Alaskan Way viaduct collapse in earthquake

Tsunami inundation of Seattle

(Seattle fault events)

Magnitude 9 Cascadia quake info and animation
posted by mwhybark at 2:56 PM on February 1

The last link visualization does appear to imply similar effects in Seattle to the first two, but also for Portland as the river traps the water.
posted by mwhybark at 2:59 PM on February 1

mwhybark, those are interesting links though they're not the article I was trying to remember.

However, amusingly enough, if I'd just let my eye travel a little further down the page, to the "Related Posts" section I would have found the very FPP and article I was trying to remember! Megaquake hits the Pacific NorthWest, posted August 26, 2011, has a link to the Outside magazine article.
posted by Greg_Ace at 4:55 PM on February 1 [1 favorite]