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Tsunamis (Read 614 times)
Sprintcyclist
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Tsunamis
Feb 28th, 2010 at 8:53am
 

This is amazing - a wave going 720 kms/hr.


I'm going to go watch it, get some piccies



Quote:
A TSUNAMI triggered by a powerful earthquake that rocked Chile is racing across the Pacific Ocean towards Hawaii and Asia at about 720 km per hour, a quake expert said.
There were already unconfirmed reports of  tsunami-related deaths on Juan Fernandez islands, off Chile, where locals would have had little time to react to warnings.

A huge arc of Pacific nations from New Zealand to Japan went on tsunami alert following the 8.8 magnitude Chilean earthquake, readying emergency plans instituted after the Indian Ocean disaster of 2004.

Hawii has declared a state of emergency.

And the tsunami has struck French Polynesia, but so far no report of major damage or casualties.

Huge waves struck the Gambier archipelago earlier today, the high commissioner's office in Papeete said, as the tsunami continued to race across the Pacific.

The Marquesas islands, northeast of Polynesia, were hit this morning by a series of two-metre (more than six feet) waves which damaged some boats but no one was hurt, officials said.

A four-metre wave hit Hiva Oa in the Marquesas later Saturday, officials said.

Schools across the region were closed, the port in Papeete was evacuated and thousands in Tahiti's hillside areas were transported from their homes to safer areas.

However many residents along the coast refused to leave, fearing lootings.

Between the waves the sea withdrew around 15 metres causing rip currents.

Sirens wailed in French Polynesia and PA systems woke up residents early Saturday to alert them about the impending waves.

The tsunami could also be as high as two metres on Rurutu in the Australes, the authorities said, while warning people to climb to at least 10 metres above sea level.

Tsunamis generally come in several waves of which the first may not be the highest.

Estimating the depth of the wave's water column to be around four kilometers on average, Roger Bilham, a professor of geological sciences at the University of Colorado, calculated that at mid-ocean, the mass of water would be hurtling toward Hawaii at 200 meters per second, or 720 kilometers per hour.

"Mid-ocean, the wave is travelling at around the speed of a jet plane,'' Professor Bilham said.

"The amplitude of the wave is small when it's mid-ocean, but it may rise to five to 10 meters when it reaches Japan or the Philippines,'' he said.

A huge arc of nations around the Pacific, from New Zealand to Japan, have gone on to tsunami alert, while sirens have sounded warnings of destructive waves around Hawaii for the first time in 16 years.

The powerful 8.8-magnitude quake that rattled Chile in the early hours of Saturday occurred offshore in a subduction zone -- the point where two tectonic plates meet and one plunges beneath the other.

The undersea earthquake that set off the 2004 Asian tsunami, which killed nearly 200,000 people and left hundreds of thousands homeless, was also a subduction earthquake.

"Subduction zone earthquakes produce the world largest tsunamis because the sea floor moves like a piston, heaving 100 kilometers by 50 kilometers or larger regions of sea floor water up or down,'' Professor Bilham said.

The US Geological Survey said the first tsunami wave was expected to hit Hawaii at around 11:19 am local time or 8.19am AEST.

"The danger can continue for many hours after the initial wave as subsequent waves arrive,'' the USGS warned.

"Tsunami wave heights cannot be predicted and the first wave may not be the largest.''

Professor Bilham expected the huge waves will smash ashore in Japan seven hours after hitting Hawaii, some time after 3pm AEST.
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Re: Tsunamis
Reply #1 - Feb 28th, 2010 at 8:19pm
 
I as at the coast, about to go for a surf when someone called and warned me about this. I probably should have gone anyway, but couldn't get much info about it where I was.

You would not be able to see or feel this sort of wave travelling at 720 km/h. It would slow down and rise up when it hit shallow water, just like any other wave.
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Re: Tsunamis
Reply #2 - Mar 3rd, 2010 at 8:23pm
 
they are bad Shocked
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Re: Tsunamis
Reply #3 - Mar 3rd, 2010 at 8:54pm
 
I have never seen a Tsunami, I have ridden waves over 5 metres high, but they sure as heck were not travelling at jet plane speed, that would be a whole different ball game.

Waves are strange things, I have been in waves 1.5 metres high, that were far more powerful than others twice as big, the volume of water, the shape, and speed, all combine and the destructive force of tsunamis is huge.

A beach could have four metre waves break on it all day, with no ill effect, but one four metre tsunami could push that four metre wall of water inland for hundreds of metres, and that is why they are scary, they do not stop at the shoreline like a well mannered swell.
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Re: Tsunamis
Reply #4 - Mar 3rd, 2010 at 9:37pm
 
A mate of mine was in a tsunami once. He had waded out to a sand bank to fish, and had to keep moving the esky up the bank over a short period of time. Obviously they got no warning or anything.
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