Indonesian tsunami early warning works, but problems remain

By Ahmad Pathoni Dec 26, 2011, 13:30 GMT

Jakarta - Indonesia has a working tsunami early warning system seven years after the Indian Ocean tsunami, but risks to coastal populations remained high, experts said.

Similar disasters that followed the 2004 tsunami have shown that a lack of preparedness and infrastructure still remained an obstacle to saving lives, one scientist said.

Danny Hilman Natawidjaja, a geology researcher at the Indonesian Institute of Sciences, said more evacuation routes and centres must be created and communications must be improved so warnings are relayed in a timely manner and those affected receive them.

He and several other scientists who have studied Sumatra's fault line predicted a giant earthquake in the West Sumatra area during the next three decades that would generate a tsunami equal to that which devastated Aceh seven years ago.

'I think if a tsunami were to hit that area now, casualties would still be high,' Natawidjaja said.

Indonesia was the country hardest hit by the December 26, 2004, tsunami, with about 170,000 deaths in Aceh province on Sumatra island.

The tsunami - which left more than 230,000 dead, 1.8 million displaced and 470,000 homes and buildings destroyed in 13 countries - was triggered by a magnitude-9.3 earthquake off Sumatra.

In response, a tsunami warning centre was established in the headquarters of the Indonesian Meteorology, Geophysics and Climatology Agency in Jakarta.

About 30 people work in shifts around the clock at the centre, monitoring giant screens showing graphics and maps.

'The warning system is working well because the core service is functioning as expected,' said Suhardjono, the head of the centre, who like many Indonesians goes by one name.

'We are capable of issuing a warning based on seismic observation less than five minutes after a major earthquake,' he said.

The early warning system consists of seismometers, ocean bottom pressure sensors, sea buoys, tide gauges and GPS instruments.

The warning centre receives and analyzes data from the sensor systems and, based on simulations and hazard and risk maps of the coastlines, can assess if a tsunami has been generated, where and when it is to be expected and which height the wave might reach.

Under the Indonesian system, a tsunami warning is issued for any undersea earthquake with a Richter scale magnitude of 7 or higher and an epicentre at a depth of less than 70 kilometres.

The death toll in the October 2010 tsunami that hit the Mentawai islands raised questions about the effectiveness of the Indonesian warning system.

The wave and the magnitude-7.7 quake off Sumatra that triggered it killed at least 431 people and displaced more than 20,000.

The centre issued a tsunami warning less than five minutes after the quake, but officials said the tsunami came too quickly and the waves would have reached the coast even before sea sensors could have detected the sudden changes in the water level to send an alarm signal.

Other officials said land-based GPS sensors and buoys to verify the existence of a tsunami had yet to be integrated into the warning system.

Natawidjaja said a network of 40 GPS sensors that he and his colleagues installed was still working independently.

'There's been a lot of progress, but I think all these years the system has relied mainly on seismic monitoring,' he said. 'It's not easy to integrate the GPS network into the warning system.'

Communications must also be improved, he said.

'When a big earthquake hit Padang in 2009, there was a power and communications blackout,' he said, referring to the magnitude-7.6 quake that killed more than 1,000 people.

'Can you imagine a worst-case scenario in which an 8.8 earthquake hits the same area followed by a tsunami 6 metres high?' he asked.

Most of the early warning system's 16 buoys have been damaged beyond repair, said Ridwan Djamaluddin, a director at the Agency for the Assessment and Application of Technology in the Research and Technology Ministry.

'Fishermen are probably to blame for the damage, but we haven't been able to arrest anyone responsible,' he said.

But the buoys have also been determined to be unnecessary, and the government is planning to install deep-sea sensors connected by cable to satellite towers on land as an alternative.

'We are testing the prototype, and we hope by 2013 this will be operational,' he said.