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Obviously you've thought of this as well, but I'll voice it anyway: if the first and fundamental assumption is accepted, then by implication the second assumption cannot hold, because if the amount of stress entering the system is near-constant, and the stress limit is also, then the time interval between ruptures ought to be more or less the same -- perhaps give or take a century or so. However, as the interval varies much more than that, we have to ask why.
Originally posted by JustMike
It's quite remarkable, really. Considering that it's only been a couple of decades since experts have even begun to develop a fair understanding of what the CSZ can do (and relatively speaking, how often), people living in the region these days have been incredibly lucky.
Magnitude 4.6 - OAXACA, MEXICO
2012 February 09 09:21:57 UTC
34.5 km (21.4 miles)
33 km (20 miles) W (264°) from Miahuatlán, Oaxaca, Mexico
Originally posted by Olivine
I have a couple of questions for the general earthquake studying community.
Based on plate tectonic theory, specifically oceanic-continental subduction zones, there seems to be a few different major mechanisms at play:
1. the "push" on the subducting oceanic plate from the associated spreading ridge.
2. the "pull" on the oceanic plate from the portion sinking into the mantle. (probably stronger on a steeply-dipping plate (ie. the Marianna trench area) vs. a shallow-dipping plate (ie. Juan de Fuca).
3. the convergent movement of the over-riding continental plate.
Take the Cascadia subduction zone, for example. The Juan de Fuca is being "pushed" by the speading ridge to its west. It's being pulled ENE by the portion diving under North America. And the NA continent is slowly moving SW over the Juan de Fuca (and Gorda) plates.
So, my questions are: Which mechanism is strongest? And which do you think is the "spark" that most often initiates a megathrust earthquake?
I can't seem to find an acceptable answer after scouring the internets. Even a proportional breakdown of relative importance would be helpful.
Just curious as to all of your thoughts...thanks in advance.
Reference Number 3656029
Universal Time February 9 2012 at 9:57:02
NZ Daylight Time Thursday, February 9 2012 at 10:57 pm
Latitude, Longitude 40.98°S, 174.87°E
Focal Depth 40 km
Richter magnitude 3.9
UTC: 2012/2/8 20:15:54
Originally posted by wasobservingquietly
reply to post by zworld
I'm always at least a day late & a dollar short! Just remembered this tonight!
I posted this back on page 27 I think it was.
It has Japan earthquakes back to January 2008. I spent a couple of hours going throught it when someone mentioned a big swarm right before the big one. Pages & pages & pages of eq's! I only found 40 of them I think it was. But the smallest I found anywhere was a 2.3. I list them in that post.
I tried to copy the post, but it copied something completely different!
There's an English option, top right. Hope this isn't too late!
Just found an English option on your HiNet link. It's up near the top right. A bright blue rectangle in the black bar.
That takes you to a list of eq's with English numbers. Only latitudes & longitudes with no place names though. Found a list of seismos, but no graphs yet. Those weren't 'clickable'. Some of the pages have English numbers, but the words aren't in English!
Some of the pages have the word 'English' option on them after you get in there farther.
Some interesting stuff in there. Even code of conduct for research activities! I just kept clicking on anything that was blue! It's after 2 AM here or I would look around some more! Hope this helps!edit on 9-2-2012 by wasobservingquietly because: Stumbled upon this!
Originally posted by murkraz
There have been at least 7 quakes in the past 3,500 years, so they're looking at 300-600 years, since the apparent date of sometime in the early 1700s. It could happen in the next 200-300 years, but imo, 200+ seems unlikely. I would give it the next 100 years, but I'm going by nothing real when I say that. The long build up might be indicating an unusually large build up of stress...edit on 9/2/12 by murkraz because: (no reason given)
TextMagnitude mb 5.4 Region MACQUARIE ISLAND REGION Date time 2012-02-09 18:52:49.4 UTC Location 58.18 S ; 157.55 E Depth 2 km Distances 1623 km SW Dunedin (pop 114,347 ; local time 07:52:49.4 2012-02-10) 1497 km SW Invercargill (pop 47,287 ; local time 07:52:49.4 2012-02-10) 1477 km SW Bluff (pop 1,938 ; local time 07:52:49.4 2012-02-10)
Magnitude mb 5.2
Region WESTERN XIZANG-INDIA BORDER REG.
Date time 2012-02-09 19:17:31.0 UTC
Location 31.04 N ; 78.41 E
Depth 10 km
Distances 85 km NE Dehra dun (pop 522,081 ; local time 00:47:31.5 2012-02-10)
35 km NW Uttarkashi (pop 17,123 ; local time 00:47:31.5 2012-02-10)
32 km NE Barkot (pop 7,725 ; local time 00:47:31.5 2012-02-10)