Publication: Sunday Sun / Extra
Paper Page:18X
Paper Date: Sun, Dec 17, 2001
Byline: Compiled by Terry Ally

When Barbadians were put on a tsunami alert last Thursday it was the first test of an early warning system which was installed six months ago to monitor the underwater volcano Kick 'em Jenny. As a result of this new system, Barbados and other Caribbean islands can expect that tsunami alerts and warnings will become a way of life just like periodic hurricane watches and warnings have become part of the Caribbean experience.

"If this monitoring system had not been in place we wouldn't have got any warning at all and the first we would have known about it was the eruptions of that Tuesday evening," head of the Seismic Research Unit Dr John Shepherd told the SUNDAY SUN. "We would have seen those anyway with the existing regional seismograph network but we would not have seen the events preceding it."

The early warning system was funded largely by the Caribbean Development Bank (CDB). The system cost $421 800 of which the CDB contributed $340 120. The balance was picked up by the Seismic Research Unit (SRU) of the University of the West Indies. It was in 1997 that the WEEKEND NATION broke the story on the underwater volcano and the potential for it to generate a tsunami (large sea  wave) that could harm virtually every country in the Caribbean basin. Within a short space of time the news spread throughout the Caribbean as other media houses ran with the story and it became a matter of public concern. In 1999 the CDB's director of projects, Desmond Brunton, confirmed to the NATION that the board had approved the grant towards the early warning system but it was only in June this year that all the instruments were installed.

Instruments

Instruments have been set up in  Grenada, Carriacou, Ile de Ronde, The Sisters, and Fort Charlotte in St Vincent. The warning centre is located at Sauteurs Observatory on the north coast of Grenada.

"Usually if the volcano is not erupting the observatory operates entirely automatically. A computer there records all the data. It is connected to the Internet from which we collect the data. When we move from yellow to orange we man the observatory and watch the volcano located nine kilometres away," Shepherd explained.

Even though volcanoes are highly unpredictable, they don't just blow up. There are indicators that something is about to happen. For example, a series of earthquakes would occur before an eruption or it could be steaming and venting gases. These events occur in swarms which increase in intensity leading to an eruption. These swarms can be measured by seismographs which calculate the intensity and location.

The SRU has established two types of seismographs on the islands around the submerged volcano. The short period measures signals every second and the broadband runs the entire spectrum. If the land around the volcano swells, then it is almost sure that an eruption is imminent. This swelling is detected by tiltmetres and Global Positioning Systems (GPS).

"Volcanoes, before they erupt on a large scale, swell up sometimes by as much as several metres and if The Sisters swell we could be in for a big eruption," said Shepherd. "With our GPS we measure the relative position of The Sisters and Ile de Rhone with respect to Grenada and Carriacou so we could see if they are going up or down. We have a precision here of better than a centimetre so it
is a very accurate technique."

Orange alert

Several weeks before Barbados, Grenada, Trinidad and St Vincent went on alert the seismographs were detecting a restless volcano. On September 12 the alert level was raised from  "green" to "yellow" indicating minor activity. These signals were picked up by the newly installed seismographs and on the basis of that information the alert level was raised to "yellow". Activity was occurring about once per week leading up to the December 4 "orange" alert when earthquake swarms peaked at about 90 earthquakes per hour.
The "orange" alert meant that eruptions could occur with less than 24 hours notice and within hours of the "orange" alert there were three eruptions.

"We can't predict earthquakes but volcanoes always give advance signals. This one didn't build up to what it might have done, but it built up high enough that we thought it was worth going up the extra alert level because it could have gone into full eruption from there," Shepherd said.

Had the ground started swelling and the tiltmetres starting inflating, then Shepherd and his team would certainly have raised a "red" alert indicating that a major eruption was imminent but that did not occur.

"Our general idea is not to panic people until they need to be," he said.

In the event that it did happen and a tsunami was generated, then a series of tidal gauges would have detected any unusual change in sea level and a tsunami warning would have been raised. Some of these gauges are owned by the SRU and others by the Barbados-based Caribbean Planning for Adaptation to Climate Change (CPACC). "We do not really have everything in position as yet but ideally we would have a map of areas that need to be evacuated and we would inform the disaster co-ordinators in the islands at risk to evacuate Area A or Area B."

Wave

If there is a tsunami people want to know where is it going to hit, how high it will be, how far inland it wil travel, how much notice will be given?

Part of the early warning system is a series of maps, which will include Barbados, showing the areas which would be inundated. It will show which parts of the coastline and how far inland the wave will travel. Those maps should be ready within the next six months. Until then, he said that Barbadians should assume that the wave will travel inland up to 17 feet above sea level.

What will this tsunami look like? Will it be a big huge wave that is every surfer's dream? Shepherd says no.

Previous eruptions of Kick 'em Jenny produced a storm-surge type wave. Essentially the tide will withdraw and a few minutes later the water will come rushing in and rise very rapidly. In some countries, the tide retreat so far out that people actually go out and pick up fish and then drown as the water rushes in.

"It doesn't roar in like a wave but the water rises rapidly maybe over five or 10 minutes. What we always advise is that if you see the sea withdrawing by an abnormal amount, even if you did not feel an earthquake, just head in the opposite direction."

It should take about 40 minutes for the wave to reach Barbados (click on the map to see details of travel times to each Caribbean island in the event of the worst case scenario of a very massive eruption).

Dome

The distance of the dome beneath the sea surface is very important because when it reaches  100 metres or less the weight of the water on it would be significantly reduced, so a major eruption would break the surface and trigger a sea wave. The summit was last measured (in 1990) at 150 metres and since then there were two eruptions which should have changed the height. In 1998 a French
ship measured it but would not give out any information. Next February or March a scientific expedition by the US National Oceanic
and Atmospheric Administration will do a detailed survey providing valuable information for scientists and disaster managers.