Re: what does trigger earthquakes ?

From: J-M Epitalon (epitalon2_at_voila.fr)
Date: 12/10/04 

Date: Fri, 10 Dec 2004 10:09:42 +0100

>
> That would explain why some micro-earthquake repeat at regular
> intervals
> of time, would not it ?
> That would also explain why injecting water triggers earthquakes in
> tectonically stable regions.
>
> Evidence please.

For the first statement, it has been recently discovered. See SAFOD
project.
(http://www.icdp-online.de/sites/sanandreas/references/references.html)

For the second,
see
http://www.glaciermedicaled.com/Earthquake_html/all_about/all_about_10.html

>
>
> That would also explain why there are some earthquakes in regions where
> there is no compressive nor shear stress...
>
> It may not be evident but there is compressive and shear stress the
> crust over. Earthquakes that occur in areas of perceived stability are
> caused by the build up of stress. It takes longer to overcome the rock
> that is less broken than in areas that are already faulted.

I meant: some earthquakes occur where the earth crust is elongated and not
compressed.
For example, the 1908 earthquake in New-Madrid, Missouri.
Other examples: mid-ocean ridge earthquakes

Jean-Marie

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