Magnitude 9.0 OFF W COAST OF NORTHERN SUMATRA; Subduction Event

[slutticus]

From the USGS Earthquake Hazards Program

http://neic.usgs.gov/neis/bulletin/neic_slav_ts.html

Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver

The devastating megathrust earthquake of December 26, 2004, occurred on the interface of the India and Burma plates and was caused by the release of stresses that develop as the India plate subducts beneath the overriding Burma plate. The India plate begins its descent into the mantle at the Sunda trench, which lies to the west of the earthquake's epicenter. The trench is the surface expression of the plate interface between the Australia and India plates, situated to the southwest of the trench, and the Burma and Sunda plates, situated to the northeast.

In the region of the earthquake, the India plate moves toward the northeast at a rate of about 6 cm/year relative to the Burma plate. This results in oblique convergence at the Sunda trench. The oblique motion is partitioned into thrust-faulting, which occurs on the plate-interface and which involves slip directed perpendicular to the trench, and strike-slip faulting, which occurs several hundred kilometers to the east of the trench and involves slip directed parallel to the trench. The December 26 earthquake occurred as the result of thrust-faulting.

Preliminary locations of larger aftershocks following the megathrust earthquake show that approximately 1200 km of the plate boundary slipped as a result of the earthquake. By comparison with other large megathrust earthquakes, the width of the causative fault-rupture was likely over one-hundred km. From the size of the earthquake, it is likely that the average displacement on the fault plane was about fifteen meters. The sea floor overlying the thrust fault would have been uplifted by several meters as a result of the earthquake. The above estimates of fault-dimensions and displacement will be refined in the near future as the result of detailed analyses of the earthquake waves.

The world's largest recorded earthquakes have all been megathrust events, occurring where one tectonic plate subducts beneath another. These include:

the magnitude 9.5 1960 Chile earthquake, the magnitude 9.2 1964 Prince William Sound, Alaska, earthquake, the magnitude 9.1 1957 Andreanof Islands, Alaska, earthquake, and the magnitude 9.0 1952 Kamchatka earthquake. As with the recent event, megathrust earthquakes often generate large tsunamis that cause damage over a much wider area than is directly affected by ground shaking near the earthquake's rupture.



The average displacement on the sea floor is estimated at 15 meters! That's insane!

[autorank]

1. Hmmm...how do you spell c o v e r u p?

"megathrust earthquakes often generate large tsunamis that cause damage over a much wider area than is directly affected by ground shaking near the earthquake's rupture." from above.

Heard that there could have been a warning out of Thailand but they relented due to the tourist industry. Any truth to that.

The authors, the US Geological Survey, are the gold-standard for vulcanology (cool term, no relation to evil Repuke "Vulcans"). It's obviously earth quake doctrine so somebody really screwed the pooch on this one. I knew there was something wrong when some minister of something or other whined about not having enough $$$'s for Tsunami warning systems. Excuse me, this article and the generally known facts about this type of quake were the warning system.

[slutticus]

7. I heard about the tourism thing.

Here's the link to that story
http://www.democraticunderground.com/discuss/duboard.php?az=show_topic&forum=104&topic_id=2874269

"Excuse me, this article and the generally known facts about this type of quake were the warning system."
Exactly. An earthquake that huge should have sent up red flags for possible Tsunamis. I think scientists in the US tried to warn people, but there isn't any infrastructure in that part of the world for distributing that info to the authorities and subsequently distributing it to the public...at least that's NOAA's exuse...
http://story.news.yahoo.com/news?tmpl=story&cid=676&e=14&u=/usatoday/20041228/ts_usatoday/scientistsinusasawtsunamicoming

I can't find any info on if the USGS tried to get any warnings out.

I will look.

[autorank]

12. I'm sure they did. They are the BEST!

They have great communications etc. and the geological scientific community is very international and interconnected. The nonsense about "detectors" was just rediculous. You really have to wade through multiple layers of bull shit in just about every story to get at a semblance of even the facts. Thanks so much for the links. They're great!

[slutticus]

13. Here's another good article.

http://www.nzherald.co.nz/index.cfm?c_id=2&ObjectID=9004878

The Australians detected the Tsunami and also tried to send warning...

[Mark H]

2. Wow!

That's a lot of earth moved there. I heard on the radio that it knocked the whole world an inch further off it's axis.

[ps1074]

3. and I've seen on TV

Scientists show satelite images of some nearby islands that have moved 30 meters from where they used to be before the quake... This is just insane...

They say the magnitude was a billion times stronger than the Hiroshima nuclear bomb.

[illflem]

4. Satellite photos also show some low lying islands

have become two or more islands as the onrush of water cut them in pieces.

[slutticus]

8. Do you guys have any links to this stuff?

That would be interesting to see.

[soothsayer]

5. USGS hides quake info these days. They didn't even post that

recent 5.6 quake off of North America (happened after the 9.0 one) until a day or so later, whereas the European equivalent posted it right away (like USGS used to). Heard tell that USGS asked Europe not to post their stuff right away, so as to give scientists a chance to study things, etc.

Oh man, it's so early for tinfoil, but WHAT ARE THEY TRYING TO HIDE????

[momzno1]

6. I wonder that myself....

but I have an alternate hypothesis. All of the fear generated by 911 served the PTB very well. Kept us calm as lambs to the slaughter. Fear of natural disaster can do the same, albeit without some of the patriotism that 911 generated. But I hope that their playing up the fear of this event in many ways indicates a distraction technique. There has been all kinds of talk about what kind of monster tsunami could be generated by an already weakened volcano in the Canary Islands off Africa breaks apart and half the volcano falls into the ocean - total wipeout of the eastern seaboard.
They frame is as "when this happens" not "if". I have heard reports of signs for evacuation routes popping up in the eastern coastal ares, where there were none before.
who knows....

Tinfoil be damned, but they are either hiding something, or they are continuing the fear tactics.

[slutticus]

10. A Tsunami in the Atlantic is a possibility.

The main disagreement on that is whether or not the waves would propagate that far. Different models of the Tsunami give varying results, some reach the US and some do not. The volcano will someday collapse into the sea, that is not disputed. But it's not like the public isn't aware of such things. I've seen many shows on PBS as well as Discovery Channel about this volcano and what could possibly happen to the east coast.

Have you heard about the Supervolcano in Yellowstone? That's the one I'm worried about. :scared:

[NMDemDist2]

14. watch the Cascade range too, St Helen's is a warning

if Mt Rainier goes, so does Seattle

[Ediacara]

15. Tides will be a major determinant for this tsunami

If the tide is going out on the east coast, the tsunami will be largely dissipated, if it's coming in, it will be greatly amplified.

ON EDIT: ya, I've heard of the Yellowstone supervolcano, it's literally in my back yard. When I suddenly move to the opposite side of the Earth.... then you should all get worried too :-)

[slutticus]

9. I wonder how well funded the USGS is.

Particularly the Earthquake division.


I'm not making excuses for them, but I don't see what they could be hiding. It's not like everyone doesn't know there was an earthquake. Also, I don't think a 5.6 event is very significant given the previous couple of days. You know how Scientists are...they're probably up to their chins in data from the 9.0 event trying to figure it all out. They probably haven't even eaten since then!

Also, I don't think the USGS posts info until they've done at least a preliminary report on the event. I'm not sure about their European counterparts.

[slutticus]

11. Check out all the aftershocks in the region.

They are all pretty intense.
http://earthquake.usgs.gov/recenteqsww/Quakes/quakes_all.html

Many of them are around 6.0! One of them was a 7.1.