What the? Geologists believe Cascadia has had EQs much larger than the 9.0 quake 300 years ago.

Unless I'm reading this wrong, apparently there is geological data to suggest that the 9.0 mega quake that happened in the pacific NW 300 years ago was considered 'average' and much larger quakes have hit that fault in the past. That's downright scary if true!

seattletimes.nwsource.com...

VANCOUVER, B.C. — Scientists are still unraveling last year's giant Tohoku earthquake and tsunami in Japan, and some of what they're finding doesn't bode well for the Pacific Northwest.

Detailed analyses of the way the Earth warped along the Japanese coast suggest that shaking from a Cascadia megaquake could be stronger than expected along the coasts of Washington, Oregon and British Columbia, researchers reported Sunday at the annual meeting of the American Association for the Advancement of Science.

"The Cascadia subduction zone can be seen as a mirror image of the Tohoku area," said John Anderson, of the University of Nevada.

Anderson compiled ground-motion data from the Japan quake and overlaid it on a map of the Pacific Northwest, which has a similar fault — called a subduction zone — lying offshore.

In Japan, the biggest jolts occurred underwater. The seafloor was displaced by 150 feet or more in some places, triggering the massive tsunami. But in the Northwest, it's the land that will be rocked hardest — because the Pacific coast here lies so close to the subduction zone.

This was the most revealing part of the article, if Cascadia is truly capable of producing an event 'twice as big' as the 9.0 event that happened there 300 years ago it's probably time to move as far away from the west coast as possible....

There's no obvious "supercyle" of supergiant quakes, as Satake suggests, in Japan. But it is clear that quakes on Cascadia have varied in size, said USGS scientist Brian Atwater. Some geologists argue the magnitude-9 quake 300 years ago was simply average and that the Northwest has been slammed by quakes twice as big in the distant past.

I'm over here and it is a bit startling. I just hope Rainier or St. Helen's don't go.

I can see both from where I'm at which means I'm not far enough away.

Well it's all relative.

Realistically a 9.2 is twice as powerful as a 9.0, the fact they say twice as big sounds deceiving. Almost sounds like they mean a magnitude 18 quake.

While a 9.2 is a devastating quake, Japan put up with a 9.0 for almost 5 minutes which is incredible.

And just because it could make a 9.2 happen doesn't mean it will. Well, it WILL, just not anytime soon.

Pred...

Originally posted by predator0187
Well it's all relative.

Realistically a 9.2 is twice as powerful as a 9.0, the fact they say twice as big sounds deceiving. Almost sounds like they mean a magnitude 18 quake.

While a 9.2 is a devastating quake, Japan put up with a 9.0 for almost 5 minutes which is incredible.

And just because it could make a 9.2 happen doesn't mean it will. Well, it WILL, just not anytime soon.

Pred...

Not anytime soon because.....??

Is it because we are so special that megaquakes will wait till we are all gone before they occur?

I thought there was an upper limit to the Richter scale. I am not positive as i am not a geologist.

Originally posted by predator0187
Well it's all relative.

Realistically a 9.2 is twice as powerful as a 9.0, the fact they say twice as big sounds deceiving. Almost sounds like they mean a magnitude 18 quake.

While a 9.2 is a devastating quake, Japan put up with a 9.0 for almost 5 minutes which is incredible.

And just because it could make a 9.2 happen doesn't mean it will. Well, it WILL, just not anytime soon.

Pred...

I assume this is the case as well. But then again who really knows what this planet is capable. Most scientists were baffled by the 9.0 quake in Japan last year and did not believe that fault was capable of anything more than a 7.5 - 8.0 quake.

Pretty sure that if a 18.0 quake ever happened it would be endgame for this entire planet.

You do have to wonder though because obviously the recorded data we have EQ's is just a small sample size and we have no clue what has happened on this planet the previous millions of years it's been in existence before humans came into the picture here.

reply to post by ButterCookie


Well there is nothing that says it will not happen tomorrow but the chances are low, a large quake only happens in the world on average once every 5-10 years. Yes, Japan had a monster but as I said in my original post, it lasted for 5 minutes which is insane, if a 9.2 happened on cascadia, the likeliness of it lasting 5 minutes too is extremely low.

The geological time scale relative to our life times is huge. 10,000 years in the geological time scale is a blink of an eye, where are to us it is quite a few generations.

We are not special as human beings and will not avoid huge natural diasasters, just look back at our history, 70,000 or so thousand years ago we had a genetic bottleneck Where we were left with as little as 15,000 humans left. Experts think it has something to do with nature or climate that impacted us, so it is obvious we have lived through large earth changes before.

Not saying humans won't see a megaquake, but this specific generation seeing it is relatively low.

Pred...

reply to post by Disconnected Sociopath


I don't think a 18 magnitude quake is possible. Scientists think that when the 6 mile long asteroid hit the earth that killed the dinosaurs it created a 12+ magnitude quake. That should say something that when a rock that big hits the earth at tens of thousands of miles an hour makes a 12 magnitude quake, that it would by hard for the earth to create anything at that size without outside influence.

While I guess it is possible, but it would be like another planet hitting us.

Pred...

Thanks for posting that article. The thing that really stuck out to me in the article was that when compared to the japan quake, more of the shaking will be on land for the pacific northwest. That is worrisome because Japan does a much better job at preparing for quakes than the Northwest in terms of having stricter building codes. It really will be a terrible day when it happens. On top of that, strong aftershocks will occur for many months. (I live on northern vancouver island). I'm about 200 ft above sea level so hopefully I will only have to deal with the shaking. I could see plenty of landslides happening, especially if it's raining a bit (it almost always rains here )

reply to post by predator0187


While I agree with you on all other points, I have to disagree about the potential length of time for a CSZ mega quake.

The leading theory is that 'when' the next 'big one' goes....this means that there is not just a quake, but an 'unzipping' of the subduction zone. When this occurs, it is projected to last for around five minutes, much like the Japan quake.

Originally posted by predator0187
reply to post by Disconnected Sociopath

 

I don't think a 18 magnitude quake is possible. Scientists think that when the 6 mile long asteroid hit the earth that killed the dinosaurs it created a 12+ magnitude quake. That should say something that when a rock that big hits the earth at tens of thousands of miles an hour makes a 12 magnitude quake, that it would by hard for the earth to create anything at that size without outside influence.

While I guess it is possible, but it would be like another planet hitting us.

Pred...

edit on 24-2-2012 by predator0187 because: (no reason given)

And like you are saying...."Scientists think" that was a 12.0 quake....Means absolutely nothing since nobody was around.....Take that statement with a grain of salt.

Hopefully nothing that big happens, but if it does......Ummmmmmm

RUNNNNNNNNNNN.....Oh wait, run to where?? We will all be dead from mass volcano eruptions and tidal waves...So enjoy life and just pray (to whoever you believe in) that nothing like this happens!!