frequency of mega-earthquakes

[parallaxicality]

Yeah yeah. Woo-sirens blaring. But that's the problem. I can't find honest scientific data on this.

As I've said, I'm working on a timeline of the far future for Wikipedia. And, like any good prediction of the future, it contains probable dates for our next few asteroid impacts and super-eruptions, but nothing on the next mega-earthquake. Of course, my search for info on mega-earthquakes is based on the assumption that they actually happen; asteroids do create giant quakes, but how much can old Momma Earth just let go in one fit of pique? Is she able to produce a 10 pointer, or is 9.5 about as high as she'll go? Is there any evidence in the geological record for a geogenic earthquake on that scale?

[Ara Pacis]

Is there even a definition for "mega-earthquake"?

[parallaxicality]

Well 10.0 or higher would be a start I suppose.

[Ara Pacis]

They dunno.

http://www.usgs.gov/faq/index.php?ac...800&artlang=en

Maybe if you can predict the layout of faultlines in the future, you'll know whether or not larger ones are possible in the future.

[dgavin]

Well, hypothetically speaking, for a 10.0 you would need a mega-thrust event along a subuduction zone, not a fault zone, thats around at least 3000km in length most likely, with the event spanning most of that trenches length. The Alutian Trench and the Atacama Trench are the only posibilities for this sort of large event. And typically the entire span of the trench does not snap back in a megathrust all at the same time. It's usualy a 200-1000km span that snaps back.

There are no known geological layer deposits I've hear of that would indicate such an event has ever happened. I'd say the likelyhood of such an event if they do occur, not related to an impact event, would be in the neighberhood of once every 1-2 billion years. If they happened anymore frequently someone would of seen depsoits in geological strata layers by now. Thats my best guess as to how often they could happen, if they do happen.