10 January 2005

How prepared is South Africa for disaster?

A geophysicist in Hawaii appears to have been the only person in the world to have realised that a massive earthquake that hit the Indian Ocean would be likely to result in a tsunami.

But because it fell out of his area of monitoring, Dr Stuart Weinstein was apparently not able to alert anyone to the threat, and despite the existence of seismology units in some of the countries where more than 150 000 people perished, modern technology could not save them.

Suddenly nature reminded people around the world of their vulnerability, and they started questioning whether enough was being done in their own countries to save them from a similar fate. But predicting what nature has in store is not an easy task.

What scientists do know is where earthquakes are most likely to strike - but when, and the magnitude of the quake, cannot be predicted.

For South Africa, the tsunami resulted in little more than some unusual currents and tides, but it was closely monitored by disaster management officials.

As soon as news of the tsunami filtered through, Dr Andrzej Kijko, the head of the seismology unit at the Council for Geoscience, made contact with the Ports Authority in Durban, warning it of unusual currents. Kijko monitored the situation every half-hour until the threat subsided.

The emergency disaster management team in Durban was also placed on alert.

The Disaster Management Act of 2002 was passed by Parliament last year and aims to prevent or reduce the risk of disaster by ensuring emergency preparedness, a rapid response to disasters and post-disaster recovery. National, provincial and municipal disaster management centres have been set up.

But the effectiveness of such plans can be measured only after the event.

Ethekwini's disaster management manager, Billy Keeves, said even the best-made plans could not anticipate a disaster of the magnitude of the Asian tsunami.

"The main issues are early warning and reliable information," said Keeves.

Once a warning has been issued, the disaster management plan is put in action. This involves a first "blue light/red light" response from emergency services, followed by engineers and others to stabilise infrastructure like electricity and water supply. Support services are then set in motion.

In Cape Town, one of the possible disasters planned for is an accident at the nearby nuclear plant at Koeberg. Franz Schlaphoff from the Cape Town disaster management unit said this included evacuation and shelter plans in the event of a nuclear disaster.

Early warning systems in South Africa include information from the weather service about potential dangerous weather patterns. The service has a network of contact numbers of disaster management centres throughout the country and SMS or email links to relative authorities.

Weather service meteorologist Siyabonga Mthethwa said that, depending on the type of system, warnings could be given two or three days in advance.

Heavy showers are detected early, but hail can be detected only two or three hours before the event.

While tsunamis may not pose a threat to South African shores, earthquakes do occur occasionally. In 2003 more than 160 earthquakes were reported in South Africa - not all of them expected.

The bulk of seismic activity in South Africa is caused by mining operations in the Gauteng, North West and Free State provinces. Networks of geophones have been installed in many of the gold mines and at other sensitive areas such as nuclear power plants.

Kijko explained that 75 percent of earthquakes occurred where the world's tectonic plates collided, and a further 25 percent occurred within the plate.

The Asian tsunami was a "textbook" example of a quake caused by plate friction, and it was just a matter of time before it occurred - and it will occur again in the future.

"We know where it will happen, but when or what size cannot be predicted," said Kijko.

Because South Africa is not an earthquake hot spot, seismologists monitor and do seismic hazard assessment for "critical structures" such as dams and pipelines.

The seismology unit has 21 stations throughout South Africa and local seismologists are able to pick up quakes from all over the world.

Kijko warned that an aftershock of up to eight on the Richter scale could still be expected; more than 1 500 aftershocks were recorded during the 48 hours following the Asian quake, and this might continue for several years.

Aftershocks are caused by energy not released during the initial quake.

3 Comments:

At 1:53 PM, Blogger Zingisile said...

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At 3:07 PM, Blogger Zingisile said...

Dr Andrzej Kijko said elsewhere that there is no risk of Tsunamis in South Africa (see - http://www.news24.com/News24/Technology/News/0,,2-13-1443_1646136,00.html). Recent events have proven that this is not true: at least two people have died on the South African coast as a direct result of the Tsunami (see http://en.wikipedia.org/wiki/Countries_affected_by_the_2004_Indian_Ocean_earthquake). Secondly, a larger death toll seems possible in future: a mid-oceanic ridge runs deep in the oceans right around South Africa, and thousands of earthquakes originating in the vicinity of this ridge have been reported over the years (see http://denali.gsfc.nasa.gov/dtam/seismic/). The possibility exists that a relatively serious earthquake of the kind that causes tsunamis could occur on this ridge. Although the wide continental shelf around South Africa is likely to reduce the impact of such tsunami, the danger exists and it is appropriate that South Africa puts in place the necessary early warning mechanisms.

 
At 4:24 PM, Blogger Melt du Plooy said...

Thank you for your post Zingisile. It makes for very interesting reading. It also makes you wonder what South Africa will do to put early warning mechanisms in place.

 

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