Not looking good.. (Haiti / Caribbean earthquakes)

[draggar]

Correct me if I'm wrong but I thought subductive plates formed volcanoes and diverging plates caused earthquakes? Just the prediction of the Cascades potential disaster had me a bit confused.

A subduction zone is where one plate is being pushed another place (like along the northern Pacific coast). Usually you'll have a much higher rate of volcanoes in this area (in the "cracks") but they can also cause mountains (the plate staying on top is being pushed back - pushing the mountains up) and the subduction earthquakes.

The plate on top can get snagged on the plate going down and get pulled down with it causing huge amounts of stress on the upper plate. When the pressure is enough, it can snap back into place. Not only is this a tremendous amount of energy being released it will push water up (subduction zones are usually under water) causing a huge tsunami. No one knows how tall the initial wave was in the 2004 earthquake / tsunami but it is believed that the actual land "snapped" up over 30 feet.

Also, most earthquakes don't happen in one place (the epicenter) - as stress is released in one section it continues along the fault line (like a crack in ice) and will go along the fault until the friction of the land can contain the energy (a.k.a all the energy is spent). If there's friction holding the land back from moving, then there will be earthquakes.

The San Andreas fault is actually two plates moving side by side. The plates moving themselves won't cause the earthquakes - it's when the stress builds up but doesn't get expelled due to friction.

Edit: 4.9 aftershock just hit Haiti (in the past hour).

Edit 2: You can now go to maps.google.com (Google Maps) and with the satellite view you can see the destruction. It wasn't like this a few days ago so they must have updated it recently.

[HYHYBT]

The thought of an earthquake scares me more then thinking about the super volcano in Yellowstone.

Well, if it makes you feel better, volcanic eruptions traditionally include earthquakes, and THAT one should have plenty of big ones before, during, and after.

Correct me if I'm wrong but I thought subductive plates formed volcanoes and diverging plates caused earthquakes?

Any joint between plates can cause earthquakes. Some faults, if I understand correctly, are even in the *middle* of a plate, though they're less active; that would be how you'd get one in, for example, Charleston. And diverging plates can cause volcanic activity as well; look at the mid-Atlantic ridge. It's just a different kind than you get at subduction zones. When the Earth's crust pulls apart, what's below it comes up.

[Bandit]

Any joint between plates can cause earthquakes.

Yep. I live in an area that gets a good 5.0 shake every now and again - and minor ones pretty regularly. Most are between 1 and 3, so almost not noticeable.

B

[Salted Grump]

Yep. I live in an area that gets a good 5.0 shake every now and again - and minor ones pretty regularly. Most are between 1 and 3, so almost not noticeable.

B

If you're in/near ottawa, the Hog's Back Falls are overdue for some plate slippage, though it did get some pressure relief around 20 years ago when there was a 'bump' around 2 miles south of Osgoode.

(Short version; My house was on top of the epicentre; it bounced six inches straight up and everyone else in the area got rattled by a 4.5)

[DGoddessChardonnay]

Quick positive note about Haiti.

Some people I know who have medical training (EMT's and such) are planning on going there to volunteer their time. I think that is awesome, and would do the same, if I had any skills that would benefit the people there. Frankly, I think I would just be in the way, and from what I understand, they are only letting people with certain skills in anyway. Which is probably a good idea.

I just logged into Facebook a while ago when I came online and found out my middle sister (who is an RN) has been in Haiti since Friday with a group to help with providing medical help to the injured.

Not sure when she's arriving back home in VA, but her last post (she's got mobile web on her phone and has been posting updates that way) said something about waiting to come home for a snack and a nap since she's working the night shift (not sure if she meant back to the hotel or wherever they're staying at down there or if they're waiting on a plane to bring them back stateside. )

Either way, what she's done is awesome. She posted yesterday she got to witness a birth and held the baby when it was born.

Even in the middle of what seems like Hell, there's a ray of hope.

[draggar]

They just had another 5.1 aftershock - and to think I was thinking the Caribbean was calming down earlier today.

Edit: and less than 30 minutes later a 4.9 aftershock.