By Laura Smith-Spark
Eighteen months after the devastating Indian Ocean tsunami, hundreds have died after a giant wave struck the Indonesian island of Java.
Their deaths have raised questions about the failure of a promised Indian Ocean tsunami early warning system to sound an adequate alert.
Some villagers say there was little or no warning ahead of the tsunami
More than 500 people died when the tsunami struck Java's southern coast on Monday.
Witnesses have said people had little or no warning to flee the 2m-high wave triggered by an undersea earthquake.
Java resident Elan Jayalani, whose village of Batukaras was one of those affected, told the BBC: "There was some confusion about the warning.
"We were told that there had been an earthquake and the tsunami might come in a couple of days... we never expected it."
The new Indian Ocean early warning system - proposed after the December 2004 tsunami which claimed 200,000 lives - was said by the UN to be "up and running" last month.
So why did a warning not reach Java's affected communities in time?
Indonesian earthquake official Fauzi told the BBC News website that although progress had been made, there were still serious shortcomings in Indonesia's monitoring systems and communications network.
Many people have been displaced after their homes were destroyed
These were compounded by the speed at which Monday's tsunami struck, said Fauzi, who works for Indonesia's Bureau of Meteorology and Geophysics (BMG).
It currently takes scientists up to 60 minutes to receive and analyse the data from 30 seismological stations and send out a warning.
With only a 20-minute interval between the magnitude 7.7 undersea earthquake and the arrival of the waves on shore, there was just no time to warn people, Fauzi said.
However, work is under way to improve the system.
- Thirty more seismological stations are to be installed this year
- A total of 160 will be in place when the network is completed in 2009, cutting the time taken to receive and process earthquake data to less than five minutes
- At present two ocean pressure sensors - part of the Deep-ocean Assessment and Reporting of Tsunami (Dart) system - are in place. Another 15-20 Dart buoys are planned by 2009
- Four land-based tide gauges are now in place in Aceh, Nias island, Padang and Bali. An international network spanning the Indian Ocean continues to be updated and expanded
The final part of the jigsaw is getting the warning message from tsunami monitoring centres to Jakarta and - in a matter of minutes - to often isolated communities.
It is in this area that Koichiro Matsuura, director-general of the UN's scientific and cultural organisation Unesco, acknowledges work remains to be done.
While the new warning system had "functioned well" in terms of information reaching Indian Ocean governments, he said in a statement, the authorities had to ensure that messages "make the final mile to the people on the coast".
"The system still has big gaps, notably in getting the warning to coastal communities in time," he said.
Fauzi also believes communications are an issue. "We don't have the systems yet so what we do is call by telephone. But sometimes the lines are busy and it's very difficult to get through.
"We need to set up an exclusive communication system because otherwise it's going to be the same problem. If we use public communication systems, it's not going to work very well."
In the meantime, officials were making use of SMS messages to contact communities at risk, he said.
Networks of sirens are also being set up this year in the Aceh, Padang and Bali regions to alert people who may be too poor to own TVs, radios or mobile phones. Another is to be built in Java next year.
Educating vulnerable coastal communities so they know how to react if an earthquake strikes or a tsunami warning is issued is also key.
When the waters receded before the giant waves hit Java's coast, witnesses reported people running on to the exposed seabed to look - a reaction that cost many lives in the 2004 tsunami.
It remains difficult to get warning messages to all vulnerable people
Charles McCreary, director of the Pacific Tsunami Warning Center in Hawaii, told BBC News that, despite improvements in warning systems, basic safety messages had still not reached everyone.
"The strategy has always been that if you're near the ocean and you feel a strong earthquake, that is your warning and you need to move to high ground or inland as quickly as possible.
"But that's a hard thing to keep up that level of awareness and to have people be able to react quickly when an event occurs - and it looks that there was a failure of that today."
Financial help continues to come from governments and organisations including Germany - a partner in building the Dart system - Japan, China and the UN, Fauzi said.
But, he added, establishing such a complex new monitoring system inevitably "takes time".
"Also, right now, there are difficulties with our human resources because this is our first experience of setting up a tsunami system," he said.
"What we need is to ask the developed countries also to assist us with expertise."
INDONESIA TSUNAMI WARNING SYSTEMS
Germany, Japan, China and the United Nations, among others, are contributing towards Indonesia's tsunami warning system
Between 15 and 20 Dart buoys are expected to be in place by 2009
Indonesia also has 30 seismographic stations and plans 30 more by end of 2006, 160 by 2009