Geology Of The Disaster

[Richard W]

There's a map of the plates involved in the 'Sumatra-Andaman Islands Earthquake of 26 December 2004':

It does not agree with Dave Yo's description:

<{POST_SNAPBACK}>

after some small studying on those plates involved, you have 3 of them squeezing each other all the way around.

The India and Burma plates are collliding. The Burma plate is actually tearing away from the Sunda plate, which carries the southern half of Thailand and the East Indies.

  It is very much possible the entire plate moved 100 feet, thus moving everything 100 feet including the islands and land involved in with that particular plate.  With the Indian plate being the largest part, it is like something as follows as a mere description

<snip>

Once that Burma plate gets small enough there will be a gigantic earthquake once the australian plate meet with the Indian plate and that back plate being part of Sumatra meet and the Burma plate disappearing completely under the Indian plate.

The Indian and Australian plates have been in contact since the days of the dinosaurs. They were both part of Gondwanaland.

The Indian plate is actually diving under the Burma plate.

Everything surrounding this part of the region will be completely destroyed and it includes all of Thailand , Cambodia and perhaps Vietnam, and Indonesia will suffer huge massive wipeouts.

Possibly turned into an analogue of the Tibetan plateau. But note that the Indian and Eurasian plates have already collided, and that the join passes through Burma. This collision did cause the Himalayas, though there may well be part of the (oceanic) Tethys plate under there. (I am not sure about the Tethys part.)

This will be felt even in Russia and China and perhaps as far as Europe.  Australia will feel it as well as Taiwan, Japan and the Phillipines which is also going to get practically wiped out from a Wave so huge perhaps maybe a mile high up or higher by the time it hits the American coasts.  A mile high of water will go inland perhaps as far as Sacramento in California.

Any backing for the notion of such a big quake?

The other interesting point here is we will have a brand new mountain range formed.  Those rocks are going to crunch upwards like similar to Mount Everest.

Surely this mountain range already exists? It sketches the border between Thailand and Burma.

This is a guess cause by that time all of us here will be obviously dead hundreds of years earlier.

At a rate of 61mm a year, make that millions of years earlier.

I can't help wondering if the Eastern continuation of the Indian plate, the Australian plate, is to blame. If you look at the All Earthquake List (past week only), you'll see several quakes on the Australian plate. For posterity, the relevant section of the list is:

5.8 2004/12/26 03:17:50 7.169 92.911 10.0 NICOBAR ISLANDS, INDIA REGION

5.9 2004/12/26 03:08:41 13.703 93.049 10.0 ANDAMAN ISLANDS, INDIA REGION

5.9 2004/12/26 02:59:11 3.194 94.325 10.0 OFF THE WEST COAST OF NORTHERN SUMATRA

6.0 2004/12/26 02:51:59 12.494 92.582 10.0 ANDAMAN ISLANDS, INDIA REGION

5.9 2004/12/26 02:36:06 12.180 92.971 10.0 ANDAMAN ISLANDS, INDIA REGION

5.8 2004/12/26 02:34:49 4.008 94.168 10.0 OFF THE WEST COAST OF NORTHERN SUMATRA

5.9 2004/12/26 02:22:01 8.813 92.537 10.0 NICOBAR ISLANDS, INDIA REGION

5.8 2004/12/26 02:15:57 12.350 92.543 10.0 ANDAMAN ISLANDS, INDIA REGION

5.9 2004/12/26 01:48:46 5.387 94.441 10.0 NORTHERN SUMATRA, INDONESIA

6.2 2004/12/26 01:21:18 6.372 93.363 10.0 NICOBAR ISLANDS, INDIA REGION

9.0 2004/12/26 00:58:50 3.244 95.825 10.0 OFF THE WEST COAST OF NORTHERN SUMATRA

4.7 2004/12/25 23:25:08 1.307 127.420 157.8 HALMAHERA, INDONESIA

4.1 2004/12/25 22:48:21 15.140 -92.309 125.3 CHIAPAS, MEXICO

5.2 2004/12/25 22:25:40 -19.102 167.761 35.1 VANUATU REGION

4.0 2004/12/25 22:20:47 -5.995 127.644 347.6 BANDA SEA

4.3 2004/12/25 20:22:19 34.425 32.103 39.0 CYPRUS REGION

4.6 2004/12/25 18:17:33 -6.220 151.081 63.5 NEW BRITAIN REGION, PAPUA NEW GUINEA

2.7 2004/12/25 17:44:20 63.418 -145.084 1.0 CENTRAL ALASKA

3.1 2004/12/25 15:57:09 63.244 -151.332 10.0 CENTRAL ALASKA

3.7 2004/12/25 09:25:08 57.527 -152.421 200.0 KODIAK ISLAND REGION, ALASKA

2.5 2004/12/25 01:56:48 62.088 -148.185 30.0 CENTRAL ALASKA

2.8 2004/12/25 00:20:06 62.949 -150.439 90.0 CENTRAL ALASKA

4.5 2004/12/24 23:54:50 -6.597 109.247 277.0 JAVA, INDONESIA

5.3 2004/12/24 19:36:38 -19.210 167.757 32.7 VANUATU REGION

2.5 2004/12/24 18:32:56 35.693 -121.016 8.8 CENTRAL CALIFORNIA

2.7 2004/12/24 18:29:47 60.175 -152.614 90.0 SOUTHERN ALASKA

2.5 2004/12/24 18:02:12 60.880 -147.637 15.0 SOUTHERN ALASKA

4.6 2004/12/24 13:49:56 -20.055 -178.843 600.0 FIJI REGION

5.2 2004/12/24 13:39:44 -20.151 -178.765 615.5 FIJI REGION

4.4 2004/12/24 13:32:17 -20.142 -178.645 600.0 FIJI REGION

3.0 2004/12/24 08:47:38 59.664 -153.070 120.0 SOUTHERN ALASKA

5.4 2004/12/24 05:31:45 -50.120 161.358 10.0 NORTH OF MACQUARIE ISLAND

2.8 2004/12/24 03:29:29 60.394 -151.315 60.0 KENAI PENINSULA, ALASKA

3.1 2004/12/24 03:14:49 32.094 -116.428 6.0 BAJA CALIFORNIA, MEXICO

2.6 2004/12/24 02:29:29 19.392 -155.249 3.3 ISLAND OF HAWAII, HAWAII

2.6 2004/12/23 23:48:23 60.211 -153.221 200.0 SOUTHERN ALASKA

3.4 2004/12/23 20:21:49 60.274 -152.551 112.5 SOUTHERN ALASKA

3.3 2004/12/23 15:49:50 35.532 -120.799 4.9 CENTRAL CALIFORNIA

8.1 2004/12/23 14:59:04 -50.240 160.133 10.0 NORTH OF MACQUARIE ISLAND

The quakes north of MacQuarie Island are on the boundary of the Australian and Pacific plates. The one in Java will be deep in the subduction zone as the Australian plate slides under the Sunda plate, and the big one of the 26th is close to the meeting point of the Indian, Australian and Sunda plates. It as though the Australian plate had an itch and accidentally set off the motion along the Indian-Sunda boundary!

Incidentally, when did the tsunami strike Phuket? I've seen so many different times cited that I no longer know what to believe. From the Thaivisa records, we know the big earthquake had been felt in Bangkok by 01.15 UTC (= GMT, possibly give or take a second or two).

[taxexile]

from the uk daily telegraph online

The Earth wobbled on its axis by about an inch

By Roger Highfield, Science Editor

(Filed: 29/12/2004)

The earthquake made the Earth wobble on its axis by an inch or so, altered regional geography by a few metres and cut the length of the day by a few millionths of a second.

 

It struck where one plate corresponding to the Indian Ocean floor is being pushed under another, Eurasia, along a long fault line known as a subduction zone.

At the fault, which stretches from the seabed to a few miles beneath the ocean floor, the two plates slipped violently and abruptly over a 700-mile stretch.

Based on calculations by Dr Chen Ji at Caltech, the 9.0-magnitude quake may have caused movement around the fault by 20-30 metres, according to Dr Ken Hudnut of the US Geological Survey, who added: "That is a lot of slip."

In turn, this will affect the local geography, notably subsidence that led to inundation along the coastline. "That earthquake has changed the map," he said.

"It is the permanent vertical movement along the coastline that may have had a serious human impact in this case, in that some harbours and port facilities may have been raised, lowered, or damaged such that they cannot readily be used in relief efforts."

He added: "The small islands that lie off the coast of Sumatra itself, such as Simeulue, and even possibly the Nicobar and Andaman Islands, may have moved by several tens of centimetres up to possibly several metres."

Dr Hudnut, of the Southern California Earthquake Hazards Assessment Project, said his colleagues planned to visit the area to examine the effects with the aid of the global positioning survey.

"That will take weeks or months to complete." The energy released as the two sides of the fault slipped against each other made the Earth wobble on its axis, he said. "A piece of the Earth's crust is in a different place, though relative to the mass of the Earth it is tiny and the effects, though potentially just barely observable, will be small."

Dr Ben Chao, of Nasa's Goddard Space Flight Centre, said one calculation suggested that the quake would cut the length of day by three millionths of a second and cause a pole shift of around an inch.

Another USGS research geophysicist, Dr Stuart Sipkin, agreed that the Earth would have received a "little jog", but said the islands off Sumatra would have been moved higher by the quake.

• The Richter scale, known for decades as the measure of earthquakes, is now seen as out of date and the term is no longer used by scientists among themselves.

Seismologists prefer the moment magnitude scale developed by Dr Hiroo Kanamori of Caltech. This is derived from the energy released during the ground movements that generate the earthquake.

 

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