A tsunami in the South Pacific this week has killed up to 150 people. Experts say the latest catastrophe has exposed the limitations of alert systems set up since the 2004 Indian Ocean tsunami which killed 23,000 people.
A beach littered with wreckage in the aftermath of the tsunami on the island of Samoa
At least 150 people are believed to have been killed when a magnitude-8 undersea quake triggered a tsunami on the islands of Samoa and Tonga in the South Pacific on Tuesday, devastating low-lying towns and villages.
Separately, a 7.6-magnitude quake struck close to the city of Padang, the capital of West Sumatra province in Indonesia, on Wednesday, killing more than 450 people.
The disasters have prompted renewed debate about the effectiveness of early alert systems set up since the 2004 Indian Ocean tsunami.
A pickup truck sits near a pile of wreckage on the island of Samoa
Countries across the Asia Pacific have set up a variety of early warning systems in the past four and a half years. They range from beach loudspeaker sirens to deep ocean monitor buoys to alert people of tsunamis and prompt them to seek safety on higher ground.
"Each country has some form of early alert system - for instance, New Zealand and Australia have their own systems. And countries like Fiji that don't have their own technology at least have the possibility of spreading news," Winfried Hanka, seismologist at the German Research Center for Geosciences (GFZ) in Potsdam told Deutsche Welle.
Japan ahead of the game
A few countries in the Pacific region joined forces in 1965 and since then, send information from their early alert systems to the Pacific Tsunami Warning Center in Hawaii. The center, which draws on its own seismological measurements, assesses the data - 24 hours a day.
In addition, the Indonesian capital of Jakarta is also home to a large Tsunami Early Warning Center - set up in the aftermath of the 2004 tsunami with financial help and expertise from the GFZ in Potsdam.
"Our concept is that we try to be very precise when it comes to sending out an alert. It's not just a general warning, which is normal in the Pacific," Hanka said. "Rather, we try and say what size of waves can be expected and which cities need to be evacuated. That's the aim of our system in which we rely on pre-calculated tsunami simulations."
Hanka pointed out that in addition to Hawaii and Jakarta, Japan had a sophisticated early alert system and used it to warn neighboring countries of impending disaster as well.
"The Japanese have poured a lot of resources into it. They have thousands of seismometer stations and several level meters," Hanka said. "But there too you have victims now and again - there is no way you can completely avoid it."
Alert systems plagued by limitations
Experts agree that early alert systems have limitations and are unable to cope if the tsunami is particularly powerful or fast.
Kevin McCue, president of the Australian Earthquake Engineering Society, said Tuesday's magnitude-8 quake struck too close to the islands of Western Samoa and American Samoa and was too fast to give much warning.
Experts say tsunami alert systems aren't fool-proof
"Tsunami warning systems are useless in most of the countries like Indonesia and Papua New Guinea, because the lead time is too short," McCue told news agency Reuters. "Far better to educate people to make for high ground immediately after they feel shaking that lasts more than about 30 seconds," McCue said.
Tsunamis cross open ocean at speeds up to 800 km (500 miles) an hour, eventually slamming ashore at heights of up to 30 meters (100 feet).
Hanka said that the latest tsunami had showed that the early alert system on Samoa needed improving - an effort that usually requires considerable investments. But an improved warning system would probably have been unable to prevent the recent catastrophe, he added.
Editor: Louisa Schaefer