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Tsunami science:

advances since the 2004 indian ocean tragedy

The Indian Ocean tsunami was one of the worst

natural disasters in history. Enormous waves struck

countries in South Asia and East Africa with little to

no warning, killing 243,000 people. The destruction

played out on television screens around the world,

fed by shaky home videos. The outpouring of aid in

response to the devastation in Indonesia, Sri Lanka,

Thailand and elsewhere was unprecedented.

The disaster raised awareness of tsunamis and

prompted nations to pump money into research

and warning systems. Today (Dec. 26), on the 10th

anniversary of the deadly tsunami, greatly expanded

networks of seismic monitors and ocean buoys are on

alert for the next killer wave in the Indian Ocean, the

Pacific and the Caribbean. In fact, tsunami experts

can now forecast how tsunamis will flood distant

coastlines hours before the waves arrive. But hurdles

remain in saving lives for everyone under the threat of

tsunamis. No amount of warning will help those who

need to seek immediate shelter away from beaches,

disaster experts said.

Since 2004, geologists have uncovered evidence

of several massive tsunamis in buried sand layers

preserved in Sumatran caves. It turns out that the

deadly waves aren’t as rare in the Indian Ocean as

once thought. “We had five fatal tsunamis off the

coast of Sumatra prior to 2004,” said Paula Dunbar,

a scientist at NOAA’s National Geophysical Data

Center. Over the past 300 years, 69 tsunamis were

seen in the Indian Ocean, she said. Despite the risk,

there was no oceanwide tsunami warning system in

the region. Now, a \$450 million early-alert network is

fully operational, though it is plagued with equipment

problems. Essentially built from scratch, the \$450

million Indian Ocean Tsunami Warning System

includes more than 140 seismometers, about 100

sea-level gauges and several buoys that detect

tsunamis. More buoys were installed, but they have

been vandalized or accidentally destroyed. The

buoys and gauges help detect whether an earthquake

triggered a tsunami.

Getting the warnings down to people living in

remote coastal areas is one of the biggest hurdles

for the new system. Not all warnings reach the local

level. And not every tsunami earthquake is strong

enough to scare people away from shorelines. In

Sumatra’s Mentawai Islands, a 2010 tsunami killed

more than 400 people because residents failed to

evacuate in the short time between the earthquake

and the tsunami’s arrival. The shaking was simply not

strong enough to trigger people’s fear of tsunamis,

even though islanders had self-evacuated after a

2007 earthquake, according to an investigation by the

University of Southern California’s Tsunami Research

Center. There was also no clear-cut warning from the

regional tsunami alert system.

Another hurdle is learning how to accurately

forecast reflected tsunami waves. The 2004 Indian

Ocean tsunami ricocheted off island chains, and some

of the worst flooding arrived unexpectedly late in

places like Sri Lanka and Western Australia. “I found

a boat on the middle of the road, and at that point

knew it was a tsunami,” recalls Charitha Pattiaratchi,

a University of Western Australia tsunami expert who

was driving on a coastal Sri Lankan road on Dec. 26,

2004. “I came to the conclusion that I was safe. Well,

I was wrong. Twenty minutes later there was seven

meters of water where I had been standing, and two

hours later there were still more waves coming.”

A tsunami warning can go out just five minutes

after a submarine earthquake raises or lowers the

seafloor, thus launching a tsunami. For more detailed

predictions of the wave’s impact, such as the extent

of flooding, scientists rely on data collected by

seismometers, GPS stations, tide gauges and buoy

systems, which is relayed by satellite to warning

centers. Computer models then convert the data into

detailed tsunami simulations, which are based on

more than 2,000 real-life examples.

After an earthquake, scientists with NOAA’s

tsunami warning centers now spend about an hour

working out the details of a tsunami forecast, said

Vasily Titov, director of NOAA’s Center for Tsunami

Research. The results project when the wave will

arrive at shorelines and harbors, estimate tsunamiinduced

currents and gauge the height of the waves.

The agency’s goal is to dramatically reduce that hourlong

delay. “We’re now at the point where we want to

do it in five minutes,” Titov said. That means building

out the seismic network, getting a faster response

from the sea-level sensors and speeding up the

computer forecasts. “When these three components

come together, then we can save everybody,” Titov

said.

By Becky Oskin, Senior Writer. Adapted from http://www. livescience.com/49262-indian-ocean-tsunami-anniversary. html. December 26, 2014.