Tag: tsunamis

Japan Disaster Was Two Tsunamis Rolled into One

By Valerie Ross | December 7, 2011 4:17 pm


Satellite radar data showed two wave fronts combining into a doubly tall tsunami off the coast of Japan on March 11.

The tsunami that spawned by the 9.0 earthquake off Japan this March was a disaster of massive proportions, reaching heights of over 130 feet in some areas and traveling up to six miles inland in others. Scientists at NASA and Ohio State University have now found another factor, beyond the sheer strength of the quake, that made the tsunami so ferocious: It started out as two separate walls of waves that combined to form one taller, more powerful “merging tsunami.”

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CATEGORIZED UNDER: Environment

Japan Tsunami Broke Bergs Off Antarctic Ice Shelf

By Valerie Ross | August 9, 2011 2:23 pm

What’s the News: The tsunami that deluged Japan in March was so strong that it broke off several large icebergs in Antarctica, 8,000 miles away, researchers report in a new paper [pdf]. Using satellite images, the researchers saw the tsunami causing new icebergs to split off—or calve—from an ice shelf, the first time such an event has been observed.

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CATEGORIZED UNDER: Environment

South Pacific Tsunami Caused by Two Earthquakes in One

By Joseph Calamia | August 18, 2010 6:25 pm

Originally scientists believed that one earthquake had set off the deadly tsunami that struck Samoa, American Samoa, and Tonga in September of 2009. But two studies to appear tomorrow in Nature argue that instead of one there were really two earthquakes that took place in rapid succession.

Tonga_jolt_final

For some scientists, the studies clear up odd behavior that didn’t fit with the originally blamed “normal-fault” earthquake in the Pacific Northwest.

“We knew right off the bat that something was weird about this earthquake,” says geophysicist Eric Geist of the U.S. Geological Survey in Menlo Park, Calif. Geist wasn’t involved in the current studies but has puzzled over the anomalous signs produced by the quake. “This is a very complicated event, and these studies, for me, really helped explain a lot.” [Science News]

John Beaven, lead author of one of the studies, told Nature News the researchers expected the Tongan island to move about three inches to the west as a result of the quake, but GPS showed it had moved nearly a foot east. They also expected the sea bed to drop but instead it rose, a sign of a different kind of “megathrust” quake. A separate study led by Thorne Lay confirmed signs of this alternate type of earthquake from seismic readings.

Though both studies point to two different types of earthquakes, they disagree on which earthquake came first and caused the other. Ronald Burgmann, a geophysicist at the University of California, Berkeley, who was not involved in either study says, overall, they both make a good case:

“As in all good chicken-and-egg mysteries,” he says, “there is merit to both views.” [Nature News]

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80beats: Science Via Twitter: Post-Earthquake Tweets Can Provide Seismic Data
80beats: Major Earthquakes Can Weaken Faults Around the Globe
80beats: A Major Quake Could Release Plutonium from Los Alamos Lab

Image: Mick Finn, GNS Science

CATEGORIZED UNDER: Environment

Undersea Cables Could Detect Tsunamis' Electric Signatures Before They Strike

By Andrew Moseman | January 20, 2010 6:12 pm

TsunamiEvacManoj Nair of the National Oceanic and Atmospheric Administration has devised a new possible method of detecting a deadly tsuami long before the wave crests to dangerous heights. And, in a bit of good news, much of it is already in place.

In a new study in next month’s Earth, Planets, and Space, Nair modeled the massive 2004 tsunami in the Indian Ocean and found that a tsunami picking up steam as it moves across the ocean emits a tiny electromagnetic signature of of about 500 millivolts. That’s enough to have an effect on the communication cables that stretch across the ocean floor, carrying internet messages and phone calls. The electromagnetic signal “is very small compared to a 9-volt battery, but still large enough to be distinguished from background noise on a magnetically quiet day,” said Nair [Daily Camera].

Nair says this kind of system could be a lower-cost alternative to the bottom pressure arrays that directly measure large movements of water. “What we argue is that this is such a simple system to set up and start measuring,” Nair says. “We have a system of submarine cables already existing. The only thing we probably need is a voltmeter, in theory” [Wired.com].

Oleg Godin, one of Nair’s research partners, said any small improvement could make a huge difference. “If you detect tsunamis in the deep ocean — and that’s what we’re working on — meaning far from shore, you have hours, certainly tens of minutes, to warn people,” he said. “If people are well educated, a 15-minute warning is enough to save everybody” [Daily Camera].

Related Content:
80beats: South Pacific Tsunami Kills More than 100 People
80beats: Geologists Find One Cataclysmic Tsunami in Every 600 Years of Thai Dirt
80beats: Haiti Earthquake May Have Released 250 Years of Seismic Stress

Image: flickr / epugachev

CATEGORIZED UNDER: Environment, Technology

South Pacific Tsunami Kills More Than 100 People

By Eliza Strickland | September 30, 2009 10:18 am

samoan-earthquakeThe tsunami that struck the South Pacific islands of Somoa, American Somoa, and Tongo yesterday has resulted in at least 108 deaths, according to early reports.

Experts monitoring the underwater earthquake that triggered the tsunami have issued various reports of its magnitude, ranging from 7.8 to 8.3. The powerful quake struck early on Tuesday morning, local time, as island residents were getting ready for work and school. About ten minutes after the shock, ten-foot-high waves hit American Somoa’s shore. “American Samoa is a small island, and most of the residents are around the coastline,” [said Filipo Ilaoa, deputy director of the American Samoan office in Honolulu]. “There was no warning or anything at all. By the time the alert was out of the Pacific Tsunami Warning Center, it had already hit” [The New York Times].

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CATEGORIZED UNDER: Environment

Tsunami Strikes American Samoa

By Eliza Strickland | September 29, 2009 4:55 pm

tsunamiA 8.3 magnitude earthquake in the South Pacific triggered a tsunami early Tuesday morning local time (5:48 pm Greenwich Mean Time), sending residents of the Samoan Islands running to the hills. At this time there are unconfirmed reports of scattered deaths in American Samoa. The powerful waves reportedly swept into Pago Pago, American Samoa’s capital city.

To the west, in the independent state of Samoa, at least one coastal village was leveled, according to eyewitness Graeme Ansell of New Zealand. “It was very quick. The whole village has been wiped out,” Ansell told National Radio from a hill near Samoa’s capital, Apia. “There’s not a building standing. We’ve all clambered up hills, and one of our party has a broken leg. There will be people in a great lot of need ’round here” [AP].

Related Content:
80beats: Indonesia May Face a “Supercycle” of Devastating Earthquakes
80beats: Geologists Find One Cataclysmic Tsunami in Every 600 Years of Thai Dirt

Image: flickr / epugachev

CATEGORIZED UNDER: Environment

Indonesia May Face a "Supercycle" of Devastating Earthquakes

By Eliza Strickland | December 12, 2008 10:30 am

coral SumatraWhile Indonesia is still rebuilding following the devastating 2004 earthquake and tsunami that killed more than 130,000 people on the island of Sumatra alone, scientists are warning that several other major earthquakes are likely to occur in the region over the next decades. A new study examined the growth records of coral reefs off the coast of Sumatra, and say they show evidence of repeated bursts of earthquakes that relieve pressure on the Sunda fault. A shock in 2007 may be the beginning of a new cycle, researchers say.

Says study coauthor Kerry Sieh: “If previous cycles are a reliable guide we can expect one or more very large west Sumatran earthquakes … within the next two decades” [Reuters]. As if to illustrate the point that the Indian Ocean is seismically active, reports are coming in that a 5.9 magnitude earthquake struck last night off the coast of Sumatra; happily, there have been no reports of casualties or damages, and authorities say there is no risk of a tsunami.

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CATEGORIZED UNDER: Environment

Geologists Find One Cataclysmic Tsunami in Every 600 Years of Thai Dirt

By Eliza Strickland | October 29, 2008 5:40 pm

tsunami sedimentsTwo groups of geologists have found evidence that the Indian Ocean tsunami that devastated coastal towns in Southeast Asia in 2004 wasn’t the first massive wave to pummel those shores, but the last tsunami of equivalent size occurred about 600 to 700 years ago. That long gap might explain how enough geological stress built up to power the huge undersea earthquake that launched the killer waves four years ago, researchers said [AP].

One group of researchers took sediment samples on a barrier island off the west coast of Thailand, while the other group dug into the soil in a northern region of Sumatra. The surge of a tsunami brings with it a great deal of sediment that rushes inland; the bigger the tsunami, the deeper and further inland the layer of sediment it leaves behind. In locations where those deposits aren’t disturbed by wind or running water, they can be used as a historical record of tsunami after more layers are added later [BBC News].

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CATEGORIZED UNDER: Environment
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