A Serious Discussion On The Cascadia Subduction Zone and Latest Studies

Over two years ago my interest in local quakes and volcanic activity led me here to ATS. Since then I have both written and joined in on many, many threads regarding the Cascadian Subduction Zone and surrounding areas. Most of my personal threads have been propelled by theories, some based on other scientific studies and some pure wild speculation. I have enjoyed all the input and interaction, learning more in the past two years than all my previous, self-educated time.

Lately we have had some new members that are bringing a whole new realm of education and understanding. I know there are earthquake forums, and pages on facebook, blogs, etc. I, however, have come to know and respect the 'group' here on ATS so prefer to take up my discussions here. There is such a wealth of threads in the fragile earth forum though. My own threads have hundreds of posts and I am finding myself jumping around on them...not sure where I read the last one or where to look for the newest info.

Of course, my main interest remains the Cascadian Subduction Zone. I am still updating my Washington State thread, but that is of a broader topic. TA has a current thread going about a pending quake, but it seems that it is not a welcome home (or the appropriate theme) for some of our newest scientific members. I thought it might be a good idea to begin a thread dedicated to the scientific discussion of the latest and greatest studies, articles and 'inside track' of knowledge about the CSZ that seems to be flowing right now.

This is not a thread for predictions or any of my newest and craziest theories, but for the more scientific minded that want to keep the discussion grounded. You all know I like to play in both fields, but it just gets a bit confusing when those conversations happen at the same time.

So. Perhaps I am the only one that will think this a good idea...but that's never stopped me before.

I will start us off with a couple of current articles provided on the PNSN facebook site courtesy of PNSN Director John Vidale, also a new member here on ATS that I hope will join us here.


Why we should constantly watch the deformation of the seafloor


On NW coast, potential for tsunami waves up to 100 feet now seems possible


The danger beneath Seattle: echoes of Japan




Lastly, I will start the discussion with an interesting quake off-shore Oregon today:

Magnitude 3.1
Date-Time Monday, March 12, 2012 at 11:37:21 UTC
Monday, March 12, 2012 at 04:37:21 AM at epicenter
Time of Earthquake in other Time Zones

Location 44.356°N, 124.445°W
Depth 26.1 km (16.2 miles)
Region OFFSHORE OREGON
Distances 28 km (17 miles) W (280°) from Yachats, OR
31 km (20 miles) WSW (256°) from Waldport, OR
44 km (27 miles) SW (225°) from Newport, OR
111 km (69 miles) WNW (288°) from Eugene, OR
192 km (120 miles) SW (228°) from Portland, OR

Location Uncertainty horizontal +/- 1.3 km (0.8 miles); depth +/- 0.8 km (0.5 miles)
Parameters Nph= 25, Dmin=44 km, Rmss=0.29 sec, Gp=230°,
M-type=local magnitude (ML), Version=2
Source Pacific Northwest Seismic Network

Event ID uw60386742

It's interesting, because at that location and depth, it could be coming from the subduction interface (I know, I sound impressive, but I stole that from John Vidales post on facebook ). This small of a quake isn't likely to be a fore-shock, but we really don't see too many right in the zone like this.



Please feel free to add any relevant articles and/or info that may help paint that grand picture we are all trying so hard to see!!

EDIT: Some more info on the CSZ for those members not so familiar with it!

The Cascadia Subduction Zone (CSZ) "megathrust" fault is a 1,000 Km long dipping fault that stretches from Northern Vancouver Island to Cape Mendocino California. It separates the Juan de Fuca and North America plates. New Juan de Fuca plate is created offshore along the Juan de Fuca ridge. The Juan de Fuca plate moves toward, and eventually is shoved beneath, the continent (North American plate).

Cascadia Subduction Zone......courtesy PNSN site

reply to post by westcoast


We discussed this alot in my geology classes over the last few years. My proffessor was convinced that the Juan De Fuca plate was going to jolt under the North American plate at any time now. Here is a cross section of the subduction zone and I will provide some links to information on it. I will also be looking forward to good inforation coming through in this thread as this is an intresting topic to me.

www.nrcan.gc.ca...

Subduction-thrust earthquakes or mega-earthquakes are known to be one stage of a subduction-thrust Earthquake Cycle. In the inter-seismic period between mega-earthquakes the rocks are being continuously deformed. The squeezing, stretching and uplifting of the rocks is determined in two ways: 1) by measuring the slow movement of survey points on the surface relative to survey points in the continental interior, and 2) by measuring the change in gravity with time at those same points.

www.livescience.com...

There are only two places in the United States where colliding tectonic plates could cause a major tsunami, and new studies show a new earthquake in at least one of these locations could be imminent.

The Cascadia subduction zone, a 680-mile fault that runs 50 miles off the coast of the Pacific Northwest -- from Cape Mendocino in California to Vancouver Island in southern British Columbia -- has experienced a cluster of four massive earthquakes during the past 1,600 years. Scientists are trying to figure out if it is about to undergo a massive shift one more time before entering a quiescent period.

www.quaketrip.com...

The Cascadia Subduction Zone is still active and will generate more major earthquakes in the future. Scientists have found that at least seven earthquakes around magnitude 9 have occurred over the last 3,500 years, an average of one every 500 years. But recent research has shown that many magnitude 8 quakes have shaken the area during the same period of time, bringing the average time between very large earthquakes down to 270 years.

www.oceanlink.info...

'Great' subduction zone earthquakes are the largest types. Because earthquake size is proportional to the area of the fault, and because the fault area of the Cascadia Subduction Zone is very large, an earthquake of magnitude 9.0 or greater is possible

Good Luck.. on your new Thread.
If the quality of your research is improving ,
well then this would be a
premium site
indeed for progressive, informative, analysis of earth movement explanations and scenarios.

With todays tech available, it has always come too mind that with the imaging, analysis,
of sin and phase waves,,
that a better graphic must be available somewhere that would give not only the Mg./Blast wave,,

but ALSO,, the affected area analysis of earth movement in total 3D.

ie: the eathquake./slip/displacement/ moved HORIZONTALLY along the AREA effected. in
the following directions,, W 10 meters E 3 meters N 15 meters S 30 meters,, etc,,,

would make things easier for anlaysis

Me

p.s my money is still on the "ever watch a car winshield ,,with a stone chip,,when the heat hits it?

Me.

Today's quake seems most likely to be deeper than the plate interface, although it might be on it, given the difficulty of finding the depth of an earthquakes offshore. There have been nearby earthquakes as large as M4 nearby on the interface in recent years - Anne Trehu has a Geology paper interpreting them as perhaps near creeping parts of the plate boundary.

So far as I can tell, the chance of a big earthquake in Cascadia hasn't changed based on the observed seismicity, but Chris Goldfinger has shown paleoseismic turbidite evidence for more frequent events in southern Oregon and northernmost California.

reply to post by JohnVidale


Thanks for the input!

As to the Turbidite. Do you mean that this may indicate more frequent events, or the next one to be more probable on the Southern end of the CSZ?

FYI to other members; I just added more CSZ info to the original OP. Although, I have to say that I am bummed about loosing all my pics from my old ATS image account.

reply to post by westcoast


From the movie a question,
when sensor one, got pinged,
sensor two pinged back,
and triagulated a North ward Movement?

the second Earth movement event,,?

hope i didnt lose you,, lol

Me.

just read above post ,, sorry i have too diagree, based on the visual evidence from the movie animation.

"Southern end of the CSZ"

triagulated a North ward Movement?,,

lol




just thought that too apply the movie too the
sensor's used
; can they triagulate the " split " movement? using realtime data ,
but speeded up by a factor of 30 days?,,
cause im sure that once the movement breaches the Vancover to Juneau backbone,,
well,, that would be certainly unusual.. to say the least


Me.

reply to post by westcoast


Chris says that the whole of Cascadia has broken 19 times in the last 10,000 years, and southern Cascadia only has broken another 20 times in the same interval. Since it has been 312 years since the last whole-margin earthquake, we are not "due" yet for the whole-margin event, but are "overdue" for the south-only event. With some math, this translates to 15% in 50 years chance of the former, and 40% chance of the latter. Other scientists consider that maybe there were only 10 well-documented south-only events, so the "official" probability of a south-only event is now 25% in the next 50 years.

reply to post by JohnVidale


Interesting. Thanks for the clarification. I, of course, being in the NW corner of Washington would be happy if those stats are right.

Then I think about Japan and how a Country that seems to lead the world in earthquake preparedness was caught off-guard. I really think the deep-tremors are a HUGE piece to the puzzle.

Geologist say their is a chance of an earthquake 9.0 or greater within the next 50 years in the Cascadia Zone. Many of the Oregon quakes, have been a couple hundred miles off the shoreline, near Southern Oregon. I just hope they don't come inland.

reply to post by westcoast


That backbone would be here,,

"Mount Edziza"
quote
Mount Edziza is a stratovolcano in the Stikine Country of northwestern British Columbia, Canada.
unquote

This one.
Still inactive,,
one of the few left,
i believe.
Me.

Big waving flag for your new thread, westcoast.

I needed a dedicated place to clarify my understanding of the CSZ--perfect.
Case in point, the Mag 4.1 offshore Oregon overnight.
Looking at the historic moment tensor solutions, this recent earthquake is most probably a strike-slip type, correct? Adding to the deformation of the Gorda plate, because it can't freely move under North America?
It's location looks to be near that dotted line on the map above--is that the Gorda fracturing apart from the Juan de Fuca?

Finally, does anyone have a nice map (or link to one) of the CSZ that shows latitude/longitude?

Good job Westcoast!

I don't add much but do like to jump from thread to thread learning so I am glad you started this thread....

Oh...and thanks for the video as well. Look forward to learning from all of you!

reply to post by westcoast

Good start to your thread and great that JV has joined the discussion. I have family in the area (two great sons) and so I am very eager to learn the short term hazards and from an interest in geology, the long term hazards.

I dont think your thread would be complete without mapping out the underwater volcanos that are active as well as the black smokers. I was actually the one who discovered the material in the 90s and turned it in to the UW. Our specimens are listed under P. Phelps. This triggered the funding of the submarine exploration of those zones.

I also still have one of the specimens. They feel those were birthed around 120,000 years ago. more or less lol.

reply to post by westcoast

Thanks westcoast for the thread. I have always been a fan of your threads for multiple reasons. I am in the mid-Willamette Valley in Oregon, about 50 miles inland from the coastline. Of course the Willamette Valley sits in between the Coast Range and the Cascade Range, so I take a serious interest in anything quake related in our area. In addition to just living in the area of discussion, I am in the property insurance business, and earthquakes are certainly a point of topic in my career world. I’ll keep an eye on this thread as well as your others WC, and if there is anything I can ever do to help, please don’t hesitate to let me know.

Thanks again!

Chachi

reply to post by Olivine


Not sure these images work, but it looks like the earthquake was on the Gorda ridge offshore.


Historically, as you say, most events out there have been strike-slip faulting on a transform, but ones actually on the ridge should be normal faulting.

Nice thread westcoast. With so many heavy guns here I shall watch from the side line for a bit. I am still delving into the historical events data so I shall be back later.

Originally posted by JohnVidale
reply to post by westcoast

 

Chris says... we are not "due" yet for the whole-margin event, but are "overdue" for the south-only event.

Oh, lover-ly. Good to know.

I'll be honest, however, my Spidey sense has been tingling BIG TIME regarding the CSZ. That is not something to take lightly as any one of my Facebook friends and co-workers (I'm a reporter) will tell you. I have predicted three of the last four 6+ quakes on that fault zone via Facebook. I get what I like to call the earthquake dizzies -- very scientific stuff -- and then post an alert to expect an earthquake within 48 hours. Works like a charm. I only missed one and I attribute that to a sinus affection, LOL.

Anyway, very interested in everyone's scientific viewpoint about this fault zone. Thanks for the post, fellow WestCoast-er.

Originally posted by PamelaBritton2U

Originally posted by JohnVidale
reply to post by westcoast

 

Chris says... we are not "due" yet for the whole-margin event, but are "overdue" for the south-only event.

Oh, lover-ly. Good to know.

I'll be honest, however, my Spidey sense has been tingling BIG TIME regarding the CSZ. That is not something to take lightly as any one of my Facebook friends and co-workers (I'm a reporter) will tell you. I have predicted three of the last four 6+ quakes on that fault zone via Facebook. I get what I like to call the earthquake dizzies -- very scientific stuff -- and then post an alert to expect an earthquake within 48 hours. Works like a charm. I only missed one and I attribute that to a sinus affection, LOL.

Anyway, very interested in everyone's scientific viewpoint about this fault zone. Thanks for the post, fellow WestCoast-er.

Being that I live right here in Oregon, is there any chance that I can be added as one of your FB friends? Seriously, shoot me a PM if that would be ok, as I would love to see your post 48 hours in advance of a local quake!

reply to post by PamelaBritton2U

O goody. My spidey sense just told me that the serious nature of this thread just went out the window.