When physicist Jörn Lauterjung flew to Indonesia in September 2007, as he has so often since the devastating Asian Tsunami of 2004 to help with the construction of an early warning system, he certainly did not realize that his work was about to be put to the test. Tsunamis are usually caused by earthquakes and it had previously not been possible to predict them. Jörn Lauterjung of the Helmholtz Centre Potsdam, the German Research Centre for Geosciences (GFZ), was already in Indonesia on 12 September 2007, at 1:10 p.m. Central European Summer Time, when an enormous earthquake measuring 8.0 on the Richter scale shook the sea floor off the south coast of Sumatra between the Mentawai Islands and Enggano Island. Although he didn’t feel the earthquake, five or six minutes later he saw the first warnings of a possible tsunami flickering across the television screen in his hotel room. The warning system may have been far from complete, but it had already passed its baptism of fire.
It was very clear to German scientists that a warning system of this kind had to be fast and reliable. After the cataclysmic 9.3-magnitude earthquake on 26 December 2004 it only took 15 minutes for tsunami waves to reach Aceh province in Indonesia, where they took 140,000 people to their deaths. To reduce the consequences of such disasters in the future, in early 2005 German researchers working under GFZ auspices presented proposals for a new kind of tsunami warning system, for which the German government will be making available a total of 49 million euros until March 2010. GFZ researcher Jörn Lauterjung, who is coordinating the project, is well aware of the enormous responsibility involved. Timely warnings give people in coastal regions far greater chances of surviving such a disaster.
A tsunami is usually caused by a submarine earthquake. Of all places, however, the world’s earthquake measuring network has a gap off the coast of Indonesia. It is precisely this hole that the GFZ is closing with 21 new measuring stations. Additionally, modern communication facilities have been installed to keep the earthquake stations online. However, it is extremely difficult to analyze the signals from powerful earth tremors in their immediate vicinity. GFZ researchers have therefore developed a new measuring and analysis process called SeisComP3, which has meanwhile detected and evaluated several strong earthquakes within two minutes. The first phase of the warning system now functions exceptionally well and the German software has been adopted by countries such as the Maledives, India, Pakistan, Thailand and South Africa.
However, submarine earthquakes do not always cause enormous waves. They are only created by earthquakes in which tectonic plates suddenly move up or down on the ocean floor. It used to take researchers 30 to 40 minutes to ascertain their direction of movement, and a tsunami would have already ravaged Indonesia’s coasts by the time they arrived at a result. That’s why German researchers measure this movement using the GPS satellite positioning system and stations directly along the coastline. This enables them to receive a result within five to ten minutes. Buoys at sea fitted with GPS technology also directly register the tsunami waves and transmit the relevant data to the control centre via satellite. Below the buoy, a sensor is anchored to the sea floor that detects the pressure that the enormous waves produce at that depth. These sensors were developed by the Leibniz Institute for Marine Research (IfM) in Kiel and the Alfred Wegener Institute (AWI) in Bremerhaven. The German researchers had already anchored two of these buoy and pressure sensor systems in the Indian Ocean off the island of Sumatra by the end of 2005 and it is planned to install a total of ten of these buoys and sensors by the end of 2009.
The German Aerospace Center (DLR) in Cologne has established a warning centre where all the data from the early warning system comes together in the Indonesian capital, Jakarta. In an emergency, however, the time between the detection of an earthquake and the arrival of a tsunami is barely enough to process the data and calculate where and when an enormous wave will hit the coast and what effect it will have. That’s why researchers from the Alfred Wegener Institute have developed software that determines how specific waves will behave along different sections of the coast long before an earthquake. Then, in a real emergency, the computer only needs to select the scenario that best matches the concrete situation and can then issue special warnings for the coastal areas that will soon be hit by floods. Unfortunately, this part of the system was not yet operational in September 2007 and could therefore not be tested. The test phase has now begun and as Jörn Lauterjung explains: “The fine-tuning is about to commence.”
If the duty officers at the warning centre in Jakarta decide to raise the alarm, the people at risk are warned by a variety of methods. Warnings of an imminent disaster are not only transmitted by television and radio stations, but also in the form of text messages sent to mobile phones. People without modern electronic communications are warned by sound trucks, sirens or warning flags on the beach. This “last mile” of the link between the warning centre and the people on the coast is also the most crucial part of the system. The people must be reached and they must respond in the right way. To achieve this, information sheets are distributed, courses run for teachers and students as well as training programmes for the police and fire services. A great deal still needs to be done in this area, but Jörn Lauterjung is very optimistic that this last mile can also be mastered.
