The Cascadia Subduction Zone
 

Before I start I'll get this right out, I am perfectly aware this post will interest almost no one.

I've chosen to write about this because 1. I'm a bit of an amateur geology buff 2. I was up late last night watching YouTube vids on the 21st Century Megathrust Earthquakes, Dec. 24th 2004 just off the Indonesian coast in the Indian Ocean





...and the 2011 Japan quake & tsunami. This video is a visualization map similar to but VASTLY more detailed than the above map simulation, but focusing on the quake rather than the tsunami. It opens with an explanation of the symbolism used, then there's a bit of a boring stretch between January 1 and March 9th. Then, it gets fascinating. At 1:49 there's a 7.2 quake, then the big 9.0 at 1:51. From that point forward, thousands of quakes occur for nearly the rest of 2011. This is followed by a series of graph charts underscoring the magnitude of this event






Both of these disasters occurred on subduction zones, the point at which oceanic plates meet continental plates. I live on one of these zones, the Cascadia Subduction Zone. Look at this area, it is pretty clearly a rift zone.

http://upload.wikimedia.org/wikipedi...NW-straits.jpg

There's no question in my mind that Vancouver Island and Puget Sound have over millions of years pulled away from the continent. This takes millions of cataclysmic seismic events, as did Japan and Indonesia. There is no question as to IF this immense quake will happen here, but only as to when.

The last such megathrust quake in this part of the word was January of 1700




This event could happen anytime, according to the frequency of the geological evidence it should happenanytime between the next three seconds to five hundred years from now.

The good news is that the major cities in the area, Vancouver/Victoria BC, Stattle/Everett/Tacoma/Olympia WA, and Portland/Salem/Eugene OR are not going to be substantially hit by any destructive tsunami as was so devastating in 2004/2011 (in fact Hawaii and Japan are in much greater danger from this), the major cities here are too far inland, The principle damage would be direct damage to buildings (esp. older brick-and-mortar structures) and landslides.



I think this sometimes when I'm on a major bridge. Not today, please. Not now.

Not impacted is a bit optimistic, there won't be a huge tsunami but there could be some remnants of it and shoreline areas could see loss of life from Puget Sound water, including the lowlying downtown area where Left Bank Books is located. There would also likely be cataclysmic landslides, esp. in the Everett/Mukilteo area (there's landslide issues there already even without a 9 magnitude quake).

The worst landslides could affect Portland, specifically the West Hills area directly behind downtown

http://summitvoice.files.wordpress.com/2011/05/web2.jpg


There could be a substantial loss of life in this event.

Well, it`s interesting to me, Paul! I became intrigued by physical geography when I first learned about glaciation as a child, and continental drift is about the most dynamic theory/manifestation of geology at work.
I thought these clips particularly were both creepy and mesmerising:-


Our knowledge of this stuff is advancing so fast too. Continental drift wasn`t even mentioned in the text books when I was at high school; we learned about eathquakes but there was no theory to tie the global pattern together. Now we have precise info about the Cascadia Zone and it`s 300-year-quake frequency. So, just as with climatology, we have moved from blissful ignorance to worried knowledge...

Incidently, if people on the Pacific Coast feel threatened, at least they`re not alone; East Coast residents have something to worry about too:-



Excuse the black humour , but faced with the possibility of disasters of this magnitude, what can you do ? Well, get a t-shirt like rostasi`s I guess! :laughing:

Oregon State University study on the potential impact of the next megathrust quake on the subduction zone


http://activetectonics.coas.oregonst...899_v1-rcw.pdf

Just want to say that I have been through thousands of earthquakes with 7.2 and 6.3 (the later killed 100+ people) and I did my degree in Geography and Geology. I love this shit. Let me know if you have any questions about my experiences.

OK, it's not about the Cascadian Subduction Zone, but I'm putting it here as I thought Paul at least might enjoy this light-hearted look at the oldest border in the world:-

I did, thank you