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Jakarta. In the wake of last week’s tsunami in the Mentawai Islands that left more than 400 people dead, questions are being raised about the effectiveness of the much-hyped tsunami early warning system.

The warning system for the entire Indonesian archipelago consists of sensors attached to 22 buoys out at sea.

These sensors are designed to detect large waves passing through and trigger the warning.

Ten of them were developed by Germany, eight by Indonesia, two by the United States and one each by Australia and Malaysia.

The buoy system is part of a larger tsunami warning network that also includes 160 seismographs monitored by the Meteorology, Climatology and Geophysics Agency (BMKG), as well as tidal gauges operated by the National Coordination Agency for Surveys and Mapping (Bakosurtanal).

However, officials say vandalism and technical errors have reduced the number of functioning buoys.

Of the 10 from Germany, only eight have already been installed.

“However, we’ve had to withdraw four of those because of vandalism and technical problems,” said Wahyu Pandu, from the Agency for the Assessment and Application of Technology (BPPT).

Of the remaining four, two are located west of the Mentawai Islands, and are equipped with GPS transceivers.

However, Wahyu said alerts from the two buoys were sent directly to Germany before being relayed to Indonesia.

He added that the buoys, which were the closest to the site, had not detected the tsunami in time because they were farther out to sea than the epicenter of the quake.

There is also a problem with the data they produce, he said, because they use GPS data from the sea surface when they should instead be relying on wave movements from a bottom pressure recorder.

Sutopo Purwo Nugroho, the director of disaster risk reduction at the National Disaster Management Agency (BNPB), confirmed that data from the two buoys was relayed directly to a center in Germany, which then forwarded it to the geophysics agency.

Wahyu said vandalism was a major threat to the effectiveness of the early warning system.

“We’ve also installed two US buoys in the seas west of Sumatra and south of Bali, but both have been vandalized,” he said, adding the same problem had affected the Indonesian buoys.

Seven of the eight local buoys have been installed by the technology agency, but only three are left — those near Aceh’s Simeuleu Island, Cilacap in Central Java, and Halmahera in Maluku.

“We’ve gone back and forth at least 17 times trying to fix them,” said Wahyu, who heads the operational program of the Indonesian Buoy Tsunami Warning System (InaBuoy TWS).

“Some have experienced technical problems, but most of them were vandalized.”

The technology agency is in charge of maintaining the buoys made in Indonesia, while the other buoys are the responsibility of their respective governments.

“We just provide the boats to transport the technicians out to the buoys, but unlike the German buoys, data from the others are relayed directly to our data center,” Wahyu said.

He added that control of the data center would be handed over from the BPPT to operational agencies like the BMKG, leaving it to focus on the engineering aspects of the program.

Meanwhile, the disaster management agency has also blamed the lack of communications infrastructure in the Mentawais for making it difficult to disseminate the tsunami alert to residents following the 7.7-magnitude earthquake that triggered the waves.

Wisnu Wijaya, the agency’s director for disaster preparedness, has said that while Indonesia’s “world-renowned” disaster mitigation system could predict a tsunami within less than five minutes after an earthquake, it meant nothing if the BMKG could not issue the alert in time.

“It would be useless if the warning gets out more than five minutes after the earthquake,” he said.

BMKG head Sriworo Harijanto said last week that her office issued the tsunami warning “four minutes and 46 seconds” after the quake, but withdrew it an hour later, “in line with standard operating procedures.”

She added that her agency was not responsible for ordering evacuations, and had forwarded the warning to authorities in Siberut, Padang and Padang Panjang in West Sumatra, as well as Muko Muko in Bengkulu.

All the authorities confirmed they had received the warning, Sriworo said.

“After we issue the warning, it’s the responsibility of these regional authorities to relay the warning and order evacuations,” she said.

But Sutopo said the lack of electricity and communications infrastructure in some parts of the Mentawais made it hard to warn people about the tsunami.

Wahyu said that while the current system was good enough, engineering developments were needed to perfect it.

“It’s an ongoing learning process,” he said.

“We’ve had three generations of warning systems since we first developed it in 2006.”

He said the main weakness of using a buoy was that it could only detect a tsunami if the giant wave passed through it.

Wahyu said the technology agency was also trying to address the issue of vandalism by developing a new system in which the sensors would be attached to deep-sea cables, with the other end tethered to points on some of the country’s outlying islands instead of buoys.

“We’ll keep developing the system and coming up with new ones that can complement or even override the existing one.”