Page last updated at 13:19 GMT, Thursday, 25 February 2010

Lessons to be learned from Haiti's tsunami

By Victoria Gill
Science reporter, BBC News, Portland

The water swept away some buildings along the coast (H.Fritz)
The water swept away some buildings along the coast

Through all the devastation, another small but deadly event in Haiti almost slipped under the radar.

Researchers have discovered that January's huge quake triggered a tsunami.

Along with four Haitian colleagues, Dr Hermann Fritz, a civil engineering professor from the Georgia Institute of Technology, US, travelled around the coast of Haiti gathering evidence about this wave.

He wanted to find out what had happened before the perishable evidence disappeared forever.

He had heard reports and saw evidence that a wave up to 3m high had hit some areas of the coast south of the capital following the quake near Port au Prince.

It had claimed at least three lives and engulfed buildings.

Once you see the water draw down, you really shouldn't be there taking pictures
Hermann Fritz, Georgia Institute of Technololgy

Dr Fritz presented some of his findings at the Ocean Sciences meeting in Portland, Oregon, US.

"This was a relatively small event," he told BBC News. "Most of the fatalities were due to the earthquake, but at least three victims we know of survived the earthquake and were hit by the wave."

These three victims were a father and his two young sons. They were standing close to the shore in Petit Paradis, watching the wave instead of heading for higher ground.

"And on the border [with the Dominican Republic], fishermen were taking photos and videos of the draw-down of the sea," he said.

This ominous draw-back in the water level is a classic sign that a big wave is approaching (although it should be said not all tsunamis are preceded by such behaviour).

"It demonstrated a lack of [tsunami] education," Dr Fritz said. "It was pure luck that the misinformation did not kill more people in this case."

Map of the region affected

Despite the devastation it caused, the Haiti earthquake was not of the type or magnitude usually associated with tsunamis. It had a magnitude of 7.0.

"Generally anything over 7.5 is cause for concern," explained Eddie Bernard, a tsunami researcher from the US National Oceanic and Atmospheric Administration (Noaa).

"But anything between seven and 7.5 can cause smaller, local tsunamis."

Local people reported seeing the wave (H.Fritz)
Local people reported seeing the wave

It also occurred on land and, to generate a tsunami, an event must be under the sea.

"Anything that moves the water generates a wave," said Dr Bernard. "And the deeper the event, the bigger the wave."

Dr Fritz explained that the main causes of the Haitian tsunami were "local landslides".

"But there are fault lines in this region that are in areas where you are more likely to generate a tsunami and, if you have a much bigger landslide going off submarine, you could have a much bigger wave," he said.

"In the north of Hispaniola, we have fault lines running along very deep water."

The wave was up to 3m high (H.Fritz)
This type of quake is not usually associated with tsunamis

In 1946, a Magnitude 8.1 earthquake hit the Dominican Republic, which shares the island of Hispaniola with Haiti. It produced a tsunami that killed almost 2,000 people.

In the Caribbean, Dr Bernard explained, most tsunamis were likely to be small and localised. "But there will be few exceptions," he said.

"The scientific community only has the relatively short historical record, rather than the geological record, so we don't know all of the trends."

And people in Haiti were not aware of the signs that suggested a tsunami was on the way.

Dr Fritz said: "Education is critical to local tsunamis. Once you see the water draw down, you really shouldn't be there taking pictures.

"There were no tsunami warning signs in Haiti along the beaches, that you see in some other Caribbean countries. It's vital to educate locals and tourists about what to do."

Disaster warning

But the Haitian tsunami gave scientists a chance to find out how well vital and potentially life-saving warning systems were working.

Noaa's Pacific Marine Environmental Laboratory has developed a warning system that picks up signals of tsunamis directly from the sea-floor.

It is called Dart - the Deep-ocean Assessment and Reporting of Tsunamis.

DART EARLY WARNING SYSTEM
DART early warning buoy
(1) Sensor measures pressure and sends data up to surface buoy
(2) Surface buoy also detects changes in sea level and motion
(3) Data transmitted via satellite to centre for tsunami risk assessment

If seismometers detect an earthquake, the Dart buoys will determine what is happening to sea levels, and whether a big wave might be on the way.

This information is then sent via satellite to a central location which can organise an alert.

Within 50 minutes of the Haiti earthquake, this system was able to issue an alert to other countries in the Caribbean to say that a small tsunami had been triggered, and that it was unlikely to affect them.

Dr Bernard said: "The first 30 minutes following the earthquake, we have to rely on education.

"The critical aspects of this are: do you feel the earthquake; do you see the ocean draw down; and do you hear that loud roar? If so, you should run for higher ground.

"But after the first few minutes, it's crucial that we have the technology - the measurements to avoid unnecessary evacuation and tell people when it is safe to return."

Right now, there are 50 of these Dart buoys all over the globe - four of which are in the Caribbean.

Dr Bernard says that, with 75 to 100 buoys worldwide, this system could provide global tsunami warnings within one hour.

The high water left its mark on buildings (H.Fritz)
The high water left its mark on buildings

"That's for everywhere we know that tsunamis have happened. If we wanted to go to half an hour detection, we could probably double or quadruple that number," he said.

Of course, the infrastructure needs to be in place. In Haiti, the warning came in by telephone to a police station that had already collapsed.

Noaa has provided the system and the UN is co-ordinating the participation of affected countries in the Caribbean.

"The important thing is to build on the existing infrastructure for this type of event. So in Caribbean nations, that would be storm warning systems and forecasting.

"The warning could come into a local weather centre," Dr Bernard explained.

"In some countries, including Haiti, there may not be sufficient resources to support a [specific] tsunami warning centre for something that happens so infrequently."

He said that this system was relatively inexpensive to install and operate.

"To get it down to an hour for everywhere affected would cost $50m initial investment and then 10% of that to maintain it," he said.

"That's not a terribly expensive system considering the potential savings of lives."



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