Tsunami speed comparable to clip of jumbo jet
CTV.ca News Staff
Published Friday, March 11, 2011 11:37AM EST
Last Updated Saturday, May 19, 2012 4:09AM EDT
Experts say the combination of a brawny earthquake and its close proximity to mainland Japan triggered a tsunami that advanced too quickly to warn residents about the dangers washing towards them on Friday.
The pending disaster began when the record 9.0-magnitude quake struck off Japan's eastern coast on Friday.
It was the most powerful temblor to strike the country in more than a century and it triggered a tsunami that rapidly made its way towards Japan.
Simon Boxall of Britain's National Oceanography Centre said the tsunami quickly roared through the Pacific Ocean at comparable speeds to a jumbo jet flying in the sky.
Only 10 or 15 minutes elapsed before the tsunami and its seven-metre waves hit the Japanese coast after the massive quake.
"No time to respond, no time to get to high ground," Boxall told CTV's Canada AM by telephone from Southampton, England.
In a telephone interview, Ioan Nistor, an associate professor of engineering at the University of Ottawa, told CTV.ca that if a tsunami forms in deep water "the waves travel at hundreds of kilometres per hour."
That's exactly what happened in the Pacific Ocean about 125 kilometres off the coast of Japan on Friday, where the quake struck and the tsunami was initiated.
How a tsunami begins
Nistor said a tsunami is triggered by an earthquake when the seismic trembling causes the vertical lift of water above the sea level of the ocean.
The displaced water begins to propagate into the ocean and the tsunami is on its way.
As the tsunami gets close to land, the massive wave of water breaks and advances towards the shoreline.
When it hits land it is "almost like a freight train that smashes everything in its path," said Nistor, usually in a sequence of two or three waves.
On Friday, the incoming tsunami waves carried fishing boats into Japanese cities, made cars float like fish and washed away roads, power lines and hundreds of homes.
Shakes and quakes
Before and after the tsunami came and went, the Earth continued to shake. Officials say that Japan has felt more than 50 aftershocks since the quake first hit on Friday. Many of these subsequent quakes have been of magnitude 6.0 or higher.
American Jesse Johnson was eating at a sushi restaurant north of Tokyo when the quake began.
"At first it didn't feel unusual, but then it went on and on. So I got myself under the table," Johnson said in an interview with The Associated Press.
"I've lived in Japan for 10 years and I've never felt anything like this before. The aftershocks keep coming. It's gotten to the point where I don't know whether it's me shaking or the earthquake."
The initial quake was quickly determined to be one of the worst in modern history, what Boxall described as a temblor that would rank "right up there in the top-10 earthquakes worldwide, I'm afraid."
Friday's quake was felt as far away as Tokyo, which lies hundreds of kilometers from the epicentre.
Japanese Prime Minister Naoto Kan said the quake caused "major damage" and officials have confirmed more than 130 deaths in the hours after the disasters hit. But hundreds are presumed to have perished and police in the city of Sendai say they have found at least 200 bodies.
Prior quakes, prior tragedies
The U.S. Geological Survey says the Friday's quake appears to be the most major to strike Japan since officials began keeping records in the late 1800s.
The USGS website maintains a list of historic earthquakes, including those recorded in Japan.
According to the USGS website, the worst known quake for fatalities in Japan occurred in September 1923, when 143,000 people died in a 7.9-magnitude quake. More than half the homes in the Tokyo-Yokohama area were destroyed in the disaster. The second-most deadly event occurred in June 1896, when an 8.5-magnitude quake struck off the coast of Sanriku and brought on a tsunami that killed more than 27,000 people.
Ninety per cent of the world's earthquakes occur in a range of earthquake and volcanic zones known as the Ring of Fire, which stretches around the Pacific Ocean and includes Japan.
Kevin McCue, a seismologist with the Australian Seismological Centre, said residents of other Pacific Ocean countries should take heed from the disasters in Japan and know the signs of a pending tsunami. Because there may not always be time to get a warning out to the public.
"It's one of the golden rules, I think. If you've felt a strong earthquake and it lasts more than about 30 seconds, then you should high-tail it for high land, at least 10 to 20 metres above high-water mark," McCue told CTV's Canada AM from Canberra, Australia.
With files from The Associated Press