Posted on 12/26/2004 2:09:10 AM PST by Grzegorz 246
http://www.crystalinks.com/tsunami.html
Tsunami comes from the Japanese tsu (harbor) and nami (wave). Appropriate naming, as some 80 percent of all tsunamis occur in the Pacific Ocean and Japan has suffered many, some coming from as far away as South America. Tsunamis are often incorrectly called tidal waves, but tides have nothing to do with them (though the damage may be worse if a tsunami hits at high tide).
A tsunami (pronounced tsoo-nah-mee) is a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life.
Tsunamis are unlike wind-generated waves, which many of us may have observed on a local lake or at a coastal beach, in that they are characterized as shallow-water waves, with long periods and wave lengths. The wind-generated swell one sees at a California beach, for example, spawned by a storm out in the Pacific and rhythmically rolling in, one wave after another, might have a period of about 10 seconds and a wave length of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour.
As a result of their long wave lengths, tsunamis behave as shallow-water waves. A wave becomes a shallow-water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s) and the water depth - let's see what this implies: In the Pacific Ocean, where the typical water depth is about 4000 m, a tsunami travels at about 200 m/s, or over 700 km/hr. Because the rate at which a wave loses its energy is inversely related to its wave length, tsunamis not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses.
Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created.
Large vertical movements of the earth's crust can occur at plate boundaries. Plates interact along these boundaries called faults. Around the margins of the Pacific Ocean, for example, denser oceanic plates slip under continental plates in a process known as subduction. Subduction earthquakes are particularly effective in generating tsunamis.
A tsunami can be generated by any disturbance that displaces a large water mass from its equilibrium position. In the case of earthquake-generated tsunamis, the water column is disturbed by the uplift or subsidence of the sea floor. Submarine landslides, which often accompany large earthquakes, as well as collapses of volcanic edifices, can also disturb the overlying water column as sediment and rock slump downslope and are redistributed across the sea floor. Similarly, a violent submarine volcanic eruption can create an impulsive force that uplifts the water column and generates a tsunami. Conversely, supermarine landslides and cosmic-body impacts disturb the water from above, as momentum from falling debris is transferred to the water into which the debris falls. Generally speaking, tsunamis generated from these mechanisms, unlike the Pacific-wide tsunamis caused by some earthquakes, dissipate quickly and rarely affect coastlines distant from the source area.
One of the worst tsunami disasters engulfed whole villages along Sanriku, Japan, in 1896. A wave more than seven stories tall drowned some 26,000 people. More than 30,000 people died in Java from a 1883 tsunami cause by a volcanic eruption.
Recent tsunamis
1946: An earthquake in the Aleutian islands sent a tsunami to Hawaii, killing 159 people (only five died in Alaska).
1964: An Alaskan earthquake triggered a tsunami up to 20 feet tall that killed 11 people as far away as Crescent City, California and caused more than 120 deaths in all. More on the Web.
1983: 104 people in western Japan were killed by a tsunami spawned from a nearby earthquake.
On July 17, 1998: A Papua, New Guinea tsunami killed roughly 3,000 people. A 7.1 magnitude earthquake 15 miles offshore was followed within 10 minutes by a wave some 40 feet tall. The villages of Arop and Warapu were destroyed.
I've seen a little bit on MSNBC and CNN that seems to have been filmed while it was occuring, from a little bit of a distance. Sort of looks like whitewater rapids. The problem is if you're close enough for really cool footage you likely won't survive to get your film out.
Were most of them Moe-ham-heads?
This is the height of tourist season in the area. Count of plenty of Western tourists in the casualty column. Does that make you feel better or worse?
Actually from reported toll so far most would be Hindu or Buddhist.
A chilling description is right. Wow. ping
Another freeper had heard this earlier, thanks for the link. Didn't I read recently that the polarity was/is expected to change again soon, shifting away from magnetic north? I know that's happened before in Earth's history, but I wonder if these quakes have any impact on those dynamics?
Prairie
Polarity? How about the stuff that comes out of the ground. This is literally ground breaking news.
A concern from a thread posted 2AM PST was the oil reserves in Indonesia changed from the three week earthquake surge in the region. Would it be possible for more or less oil to flow? Would it be possible for new volcanic activity? Would it be possible for new gold found? Diamond veins revealed?
Just look at the Pacific Basin, which has suffered extreme earthquakes in recent weeks in Japan and now southern Asia. And dormant volcanoes coming to life in US and Hawaii..
Cannot imagine what would happen if the next "the big one" hits off US or even Mexican or South American coast. May God Bless and Keep those who mourn, and protect us all.
I just found out that 30 or so died in Krabi, where I was 3 weeks ago. I am fairly certain that the scuba boats are lost, along with the folk I dove with.
I am just stunned by this all, it coulda been me...
Make that- dormant volcanoes coming to life in US MAINLAND as well as in Hawaii...
I want you to focus on this comment:
Re: "'ALL THE PLANET IS VIBRATING' from the quake, said Enzo Boschi, the head of Italy's National Geophysics Institute. Speaking on SKY TG24 TV, Boschi said the quake even disturbed the Earth's rotation."
But the update is providing new details of devastation, especially in areas that are hotbeds of revolution and terrorism! Reuters is reporting tsunamis hitting East Africa capsizing boats in Somalia.
Asian Quakes' Tsunami Kill More Than 7,200
25 minutes ago [around 9AM PST 12/26/04]
World - AP Asia
By LELY T. DJUHARI, Associated Press Writer
http://news.yahoo.com/news?tmpl=story&u=/ap/20041226/ap_on_re_as/indonesia_earthquake_6
[Excerpt]...The rush of waves brought sudden disaster to people carrying out their daily activities on the ocean's edge: Sunbathers on the beaches of the Thai resort of Phuket were washed away; a group of 32 Indians — including 15 children — were killed while taking a ritual Hindu bath to mark the full moon day; fishing boats, with their owners clinging to their sides, were picked up by the waves and tossed away.
"ALL THE PLANET IS VIBRATING" from the quake, said Enzo Boschi, the head of Italy's National Geophysics Institute. Speaking on SKY TG24 TV, Boschi said the quake even disturbed the Earth's rotation.
The U.S. Geological Survey ( news -web sites ) measured the quake at a magnitude of 8.9. Geophysicist Julie Martinez said it was the world's fifth-largest since 1900 and the largest since a 9.2 temblor hit Prince William Sound Alaska in 1964.
The epicenter was located 155 miles south-southeast of Banda Aceh, the capital of Aceh province on Sumatra, and six miles under the seabed of the Indian Ocean.
On Sumatra, the quake destroyed dozens of buildings — but as elsewhere, it was the wall of water that followed that caused the most deaths and devastation.
Tidal waves leveled towns Aceh province on Sumatra's northern tip. An Associated Press reporter saw bodies wedged in trees as the waters receded. More bodies littered the beaches.
Health ministry official Els Mangundap said 1,876 people had died across the region, including some 1,400 in the Aceh provincial capital, Banda Aceh. Communications to the town had been cut.
Relatives went through lines of bodies wrapped in blankets and sheets, searching for dead loved ones. Aceh province has long been the center of a violent insurgency against the government.
The worst known death toll so far was in Sri Lanka, where a million people were displaced from wrecked villages. Some 20,000 soldiers were deployed in relief and rescue and to help police maintain law and order. Police chief, Chandra Fernando said at least 3,000 people were dead in areas under government control.
An AP photographer saw two dozen bodies along a four-mile stretch of beach, some of children entangled in the wire mesh used to barricade seaside homes. Other bodies were brought up from the beach, wrapped in sarongs and laid on the road, while rows of men and women lined the roads asking if anyone had seen their relatives.
"It is a huge tragedy," said Lalith Weerathunga, secretary to the Sri Lankan prime minister. "The death toll is going up all the time." He said the government did not know what was happening in areas of the northeast controlled by Tamil Tiger rebels.
The pro-rebel www.nitharsanam.com Web site reported about 1,500 bodies were brought from various parts of Sri Lanka's northeast to a hospital in Mullaithivu district, 170 miles northeast of the capital, Colombo.
About 170 children at an orphanage were feared dead after tidal waves pounded it in Mullaithivu, the Web site said.
No independent confirmation of the report was available, but TamilNet — another pro-rebel Web site — said some guerrilla territory was badly hit. "Many parts ... are still inaccessible and it was difficult to provide damage estimates or death tolls there," it said.
In India, beaches were turned into virtual open-air mortuaries, with bodies of people caught in the tidal wave being washed ashore.
In Tamil Nadu state, just across the straits from Sri Lanka, 1,567 people were killed, said the state's top elected official, Chief Minister Jayaram Jayalalithaa.
Another 200 died in neighboring Andhra Pradesh state, 102 in Pondicherry, at least 116 people in Kerala state and elsewhere, according to the governments in each state.
"I was shocked to see innumerable fishing boats flying on the shoulder of the waves, going back and forth into the sea, as if made of paper," said P. Ramanamurthy, 40, who lives in Andra Pradesh's Kakinada town.
The huge waves struck around breakfast time on the beaches of Thailand's beach resorts — probably Asia's most popular holiday destination at this time of year, particularly for Europeans fleeing the winter cold — wiping out bungalows, boats and cars, sweeping away sunbathers and snorkelers, witnesses said.
"Initially we just heard a bang, a really loud bang," Gerrard Donnelly of Britain, a guest at Phuket island's Holiday Inn, told Britain's Sky News. "We initially thought it was a terrorist attack, then the wave came and we just kept running upstairs to get on as high ground as we could."
"People that were snorkeling were dragged along the coral and washed up on the beach, and people that were sunbathing got washed into the sea," said Simon Clark, 29, a photographer from London vacationing on Ngai island.
On Phuket, Somboon Wangnaitham, deputy director of the Wachira Hospital, said one of the worst hit areas was the populous Patong beach, where at least 32 people died and 500 were injured.
Another survivor on Phuket was Natalia Moyano, 22, of Sydney, Australia, who was being treated for torn ligaments.
"The water kept rising. It was very slow at first, then all of a sudden, it went right up," Moyano said. "At first I didn't think there was any danger, but when I realized the water kept rising so quickly, I tried to jump over a fence, but it broke."
On Phi Phi island — where "The Beach" starring Leonardo DiCaprio was filmed — 200 bungalows at two resorts were swept out to sea.
"I am afraid that there will be a high figure of foreigners missing in the sea and also my staff," said Chan Marongtaechar, owner of the PP Princess Resort and PP Charlie Beach Resort...[Snipped]
Nice tagline.
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