KEY POINTS:
In a plain single-storey building in Honolulu, Gerard Fryer brings passion to the topic of tsunamis.
"Tsunamis are seductive in that they unfold slowly," he says, seated at one of the Pacific Tsunami Warning Centre computers receiving seismic data from all around the Pacific.
The Australian is a
senior geophysicist at the centre, which is a place of importance to earthquake-prone New Zealand.
He notes that the Hikurangi trench - the deepsea trough from the Kaikoura Peninsula to East Cape - is a "significant local hazard. It could be bad news for your guys."
He speaks with a fascinated tone about tsunamis, what causes them, the damage they can inflict and the need for education and local warning systems so lives can be saved by preventive measures.
One of his major themes is stressing that the first wave may not be the largest.
"You have to be aware the hazard is there. Waves can be 10 minutes apart to over 30 minutes, so the shoreline can be dangerous for a long time. If the public knows even a little, they should do fine."
He cites the case of Tilly Smith, the London schoolgirl credited with saving 100 tourists at a Thai beach during the Indian Ocean tsunami on Boxing Day 2004.
Tilly, then 10, was on a morning walk on a Phuket Island beach when she saw "bubbling on the water ... and foam sizzling just like in a frying pan".
Just before her holidays, she had studied tsunamis in geography and recognised the unusual water conditions as a warning sign one was coming. She told her parents and alerted staff at the Marriott Hotel, where they were staying. The beach was evacuated minutes before waves struck. It was the only beach in the area where no one was killed or badly hurt.
"In half a mile of beach ... an educated public survives," says Dr Fryer.
He is one of 12 geophysicists among just 15 staff at the Honolulu facility.
The centre works closely with other regional and national bodies in monitoring seismological and sea level stations and instruments in the Pacific to evaluate whether earthquakes will be followed by tsunamis. It also acts as the local warning centre for Hawaii.
When data comes in from one of those stations about an earthquake, the staff examine the seismographic information to figure out where the epicentre is.
"With each seismogram we look at the first two minutes of information and see how much energy is released [from the earthquake] and from that we convert it to a magnitude. This is really quick and dirty, doing it all within a few minutes."
If the magnitude is less than 6.5, the centre's staff will send out a message to other observatories to let them know thy are aware of it.
"If it is between 6.5 and 7.5, we send out a tsunami information statement [to the closest areas] that a tsunami hazard is in the immediate vicinity.
"Between 7.6 and 7.8, then we say everywhere within 1000km of the epicentre should worry about a tsunami.
"If it is bigger than 7.8, everywhere that the tsunami is going to reach within three hours we give a warning, and everywhere between three hours and six hours we put in a watch [advisory]."
Additional bulletins are put out at least hourly and the warning and watch areas expanded as required.
Dr Fryer says the centre sends out messages over as many circuits as people want. "We push them out through telex ... telephone, by faxes and internet." He says email is not a preferred circuit: "You never know how fast it is going to get there."
The information the centre receives comes from tide gauges all around the Pacific and Indian Oceans, but in recent times it has been employing an ocean sensor system called Dart (Deep Ocean Assessment and Reporting of Tsunami).
"It is a little device on the ocean bottom which measures pressure; it weighs the ocean above it and if there is a long-length wave that goes over it, it will detect it and transmit an acoustic signal to a surface buoy and a coded signal is radioed up to a satellite and down to us so we can see it in real time."
There are 32 in the Pacific, many of them near the Aleutian Islands and the Gulf of Alaska. Dr Fryer says tsunamis from that region will reach Hawaii in 4 1/2 hours. "We have no land masses in between, so we don't have much time and we need the information."
The sensors were developed by the United States National Oceanic Atmospheric Administration, which runs the Pacific warning centre.
In association with the Americans, Australia recently installed a Dart sensor in the Tasman Sea, off Fiordland, and the US is understood to be planning to deploy a couple off the east and northern coastlines of New Zealand.
While the Hawaii centre warns of tsunamis coming from across the ocean, Dr Fryer says that if the earthquake occurs closer to home, a local warning system is required.
He can't stress enough how important they are, but says "it's up to local government how to spend their money".
For areas without organised systems, he says there is a "natural" warning in the earthquake itself.
In the Indian Ocean earthquake that the UN estimates claimed 230,000 lives, 100,000 died in Sumatra. Simple precautions such as moving inland and climbing trees would have saved many of the people, but they did not know what to do.
- NZPA
