The crucial 5 minutes

That was the crucial difference when compared to the devastating tsunami of December 2004. When the meter-high waves crashed into the coastline, there were no warnings whatsoever. Almost a quarter of a million people lost their lives, Banda Aceh looked like a wasteland. “It was clear to us that we had to do something”, says Jörn Lauterjung. A huge challenge began at that time for the geo-scientist at the Helmholtz Centre Potsdam, the German Research Centre for Geo-Sciences (GFZ). As project leader for a team from nine German research facilities, it was his responsibility to construct a tsunami early-warning system in the Indian Ocean; respective funding for this came from the aid fund for the tsunami victims. Lauterjung was confident from the beginning despite all of the challenges, “We had the technology to help the people on site.”

It is an ingenious system that was developed by geo-scientists, oceanographers and IT experts specifically for the conditions in the Indian Ocean. More than 160 seismometers distributed through the entire country, as well as GPS satellite sensors constantly provide real-time data; in addition to that, we have tide-gauge stations along the coast and on the offshore islands to monitor the sea level. The data all flows into a specially-designed warning system in Indonesia’s capital-city Jakarta. Scientists there monitor the Indian Ocean day and night – the high-tech headquarters represent the centrepiece of the early-warning system with the name “German-Indonesian Tsunami Early-Warning System” – abbreviated GITEWS.

The technology is precisely configured to detect tsunamis as they occur; they are almost always activated by a strong earthquake on the seabed. Two tectonic plates come together off the Indonesian coast; the Indo-Australian Plate is slowly creeping several centimetres underneath the Eurasian Plate every year, which repeatedly results in strong earthquakes. A dense network of earthquake-stations thus forms the core of the early-warning system. The seismometers are distributed in such a manner that an earthquake can be detected within two minutes by at least three stations. The more precisely the staff at the warning-centre can identify the location and strength of the earthquake, the better they can predict when and where a tsunami could arrive. But not every strong earthquake automatically generates a tsunami as its consequence. The data from the seismometers on their own cannot provide information whether or not a tsunami will occur. By means of GPS, the warning system therefore receives additional information regarding the direction in which the seabed is shifting. It is only when the seabed actually rises during an earthquake that it displaces the mass of water located immediately overhead. A tsunami consequently spreads out in the form of a ring on the surface of the ocean. Conversely, if the seabed merely shifts to the side, the wave fails to appear – this is why the earthquake off the coast of Sumatra in 2012 turned out to be so harmless.

“Even if an early warning system is incredibly sophisticated, fatalities will still never be completely avoidable.”

But despite the previous success of GITEWS, Jörn Lauterjung is aware of the limitations of the tsunami prognoses; ”Even if an early warning system is incredibly sophisticated, fatalities will still never be completely avoidable.”  Evacuations in Indonesia are extremely complicated, since the country consists of more than 17,000 islands with long coasts, and the roads are, in part, poorly built. This is why evacuation exercises take place annually, and people are trained in proper behaviour for a tsunami. A considerable contribution is offered by the employees of relief agencies. The international Diakonie Catastrophe Aid organisation, for example, works together with locals in high-risk tsunami regions to make precautionary measures and equips them with alarm devices. Flood-risk maps have also proven to be reliable, in which dangerous areas, escape routes and shelters are marked. Inhabitants should be able to recognize early signs of a tsunami, such as retreat of the water, and initiate warnings and evacuation for other endangered citizens”, says Caroline Hüglin, who coordinated the Diakonie Catastrophe Aid project in Sumatra until 2007. Once people know how tsunamis work, this is the most effective protective measure because of the short window of opportunity after the warning signal – she is convinced of this.
 
Indonesia has in the mean time acquired the status of a Regional Tsunami Service Provider and warns other involved countries in the region when a tsunami is imminent. They are thus able to relieve the technicians in Japan and the US, who had thus far been in charge of tsunami monitoring in the Indian Ocean. In the future, perhaps the limitation of five minutes prior to the warning can be reduced. Jörn Lauterjung from the GFZ is optimistic that tsunami early-warning systems can become faster. It is conceivable for example, he says, that additional sensors and satellites could be deployed to fortify the detection network. In the end, however, there are physical limitations for what is technically feasible, because earthquakes are not predictable, “Something has to move first before we can measure it.”