Thursday, February 14, 2008

More SRL on cratons


You gotta love cratons! They are the oldest crust on earth, and a source of all the diamonds, and other deep minerals.

This paper makes the proposition that there is something special about the outer edges of cratons, that makes them prime areas for earthquakes. This makes sense, since if they are general stronger than the surrounding rock, then things crush up against them, like an icebreaker in pack ice.

It starts with my most favourite picture, that of the New Madrid seismicity.

Note the big thrust zone in the centre, and the two shear wings. This is the Mama of all such zones, which would be proven if only they had decent seismic monitoring (1 km accuracy) in our ENA zones. In the 1800's all three 'wings' let go in a short time!

Now, they plot it in relation to the world, and also zooming in on North America.

You'll have to click on it to get more detail. Our favourite seismicity areas (Ottawa and Hamilton) are more in the interior, but still look related. I just tend to think they cluster on the edge because that's where the craton got the most beat-up during the Wilson Cycles.

5 comments:

Harbles said...

So a nuclear waste repository in an abandoned diamond mine in a Kimberlite Pipe would be:

A) a good idea

B) a very poor idea

??

Harold Asmis said...

Not a good idea, since it would be a prime mining site for diamonds! And there's the usual crap about future ignorant generations mining, etc.

Generally you want to locate in areas of no economic importance.

Harbles said...

Which implies the expense of digging your own hole. So ok just outside the economicly significant are but still central in a craton?

Harbles said...

And lets pretend I have given you a $500,000 over 24 months contract to determine this answer.

LOL!

:)

Harold Asmis said...

I spent most of my life figuring out the answer, but nobody is listening! Still, it was fun. I'm trying to dig up some open source analysis software to get back into the game, but, oh, my brain hurts!