[meteorite-list] NASA Finds 'Merging Tsunami' Doubled Japan Destruction

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 5 Dec 2011 17:47:52 -0800 (PST)
Message-ID: <201112060147.pB61lqaB029896_at_zagami.jpl.nasa.gov>

Dec. 5, 2011

Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole at nasa.gov

Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0474
alan.buis at jpl.nasa.gov

RELEASE: 11-405

NASA FINDS 'MERGING TSUNAMI' DOUBLED JAPAN DESTRUCTION

WASHINGTON -- NASA and Ohio State University researchers have
discovered the major tsunami generated by the March 2011 Tohoku-Oki
quake centered off northeastern Japan was a long-hypothesized
"merging tsunami." The tsunami doubled in intensity over rugged ocean
ridges, amplifying its destructive power at landfall.

Data from NASA and European radar satellites captured at least two
wave fronts that day. The fronts merged to form a single, double-high
wave far out at sea. This wave was capable of traveling long
distances without losing power. Ocean ridges and undersea mountain
chains pushed the waves together along certain directions from the
tsunami's origin.

The discovery helps explain how tsunamis can cross ocean basins to
cause massive destruction at some locations while leaving others
unscathed. The data raise hope that scientists may be able to improve
tsunami forecasts.

Research scientist Y. Tony Song of NASA's Jet Propulsion Laboratory in
Pasadena, Calif., and professor C.K. Shum of The Ohio State
University discussed the data and simulations that enabled them to
piece the story together at a media briefing Monday, Dec. 5, at the
American Geophysical Union meeting in San Francisco.

"It was a one in 10 million chance that we were able to observe this
double wave with satellites," Song said. He is the principal
investigator in the NASA-funded study.

"Researchers have suspected for decades that such 'merging tsunamis'
might have been responsible for the 1960 Chilean tsunami that killed
about 200 people in Japan and Hawaii, but nobody had definitively
observed a merging tsunami until now," Song said. It was like looking
for a ghost. A NASA-French Space Agency satellite altimeter happened
to be in the right place at the right time to capture the double wave
and verify its existence."

The NASA-Centre National d'Etudes Spaciales Jason-1 satellite passed
over the tsunami on March 11, as did two other satellites -- the
NASA-European Jason-2 and the European Space Agency's EnviSAT. All
three carry radar altimeters, which measure sea level changes to an
accuracy of a few centimeters. Each satellite crossed the tsunami at
a different location, measuring the wave fronts as they occurred.
Jason-1 launched 10 years ago this week on Dec. 7, 2001.

"We can use what we learned to make better forecasts of tsunami danger
in specific coastal regions anywhere in the world, depending on the
location and the mechanism of an undersea quake," Shum said.

The researchers think ridges and undersea mountain chains on the ocean
floor deflected parts of the initial tsunami wave away from each
other to form independent jets shooting off in different directions,
each with its own wave front.

The sea floor topography nudges tsunami waves in varying directions
and can make its destruction appear random. For that reason, hazard
maps that try to predict where tsunamis will strike rely on sub-sea
topography. Previously, these maps considered only topography near a
particular shoreline. This study suggests scientists may be able to
create maps that take into account all undersea topography, even
sub-sea ridges and mountains far from shore.

Song and his team were able to verify the satellite data through model
simulations based on independent data, including GPS data from Japan
and buoy data from the National Oceanic and Atmospheric
Administration's Deep-ocean Assessment and Reporting of Tsunamis
program.

"Tools based on this research could help officials forecast the
potential for tsunami jets to merge," Song said. "This, in turn,
could lead to more accurate coastal tsunami hazard maps to protect
communities and critical infrastructure."

For more information about presentations at the American Geophysical
Union meeting, visit:

http://www.nasa.gov/agu
        
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Received on Mon 05 Dec 2011 08:47:52 PM PST