New scientific methods and novel technologies distinguish this system from previous tsunami warning systems. Previously used systems, such as the Pacific Tsunami Warning System, are not optimal for Indonesia due to its distinctive geological situation. The earthquakes in the Indian Ocean off the coast of Indonesia occur along a subduction zone, the Sunda Trench, which arches from the northwestern tip of Sumatra to Flores in eastern Indonesia. If a tsunami is generated here, the waves will, in extreme cases, surge up the coast within 20 minutes, leaving only very little time for an early warning. This limiting factor was therefore the basis of the concept for the whole system.
Technical concept of GITEWS
Current status of the project
The German-Indonesian Tsunami Early Warning System for the Indian Ocean (GITEWS) was in its entirety handed over to Indonesia on 29 March 2011 and has demonstrated its full functionality during several strong earthquakes and tsunami. Tsunami warnings are issued in less than five minutes after a sea quake, followed by updates or cancelation messages.
GITEWS has been completed successfully. It can warn or give the all-clear very quickly and accurately, and its expandability for the entire Indian Ocean is part of this development work. In the warning center in Jakarta based at the Indonesian Meteorological, Climatological and Geophysical Agency BMKG, about 30 people work in shifts around the clock. The system was internationally evaluated and classified as one of the most advanced tsunami warning systems worldwide.
The geological situation in Indonesia with extremely short periods (30 to 40 minutes) between an earthquake and the arrival of a tsunami on the coast called for an entirely new approach to the design of tsunami early warning. The system is based on more than 300 different land-based sensor systems. The warning is based on very fast and precise recording and evaluation of earthquakes, which forms the core of the warning system. The rapid determination of earthquake parameters (location, depth, magnitude) via 160 seismometers on land is the first and most important foundation for a tsunami preview by means of modeling, as well as the generation of a warning message that is based on the preview. This first assessment of the situation is subsequently verified by GPS data from continuously GPS stations and tide gauges along the coast of Indonesia. The tsunami itself is detected by the tide gauges via pressure, radar- and floating sensors.
The development of the entire system was continuously supplemented with the latest research results. Using the seismological analysis system SeisComP3, it was therefore possible to develop a new, rapid and robust method for the determination of earthquake parameters, which is now used in virtually all countries bordering the Indian Ocean and other countries around the world (a total of approximately 40 nations use SeisComP3). Another completely new approach is the use of GPS measurements for the precise determination of the deformation of the earth crust, from which conclusions about the rupture mechanism and thus a possible tsunami formation can be recorded very quickly.
The innovative conceptual design of the system allows an evaluation of measurement data from all sensors in the shortest possible time so that a reliable tsunami warning may be released in less than five minutes. Consequently, an advance warning of about 30 minutes remains for the main Indonesian islands. The islands offshore Sumatra along the Sunda Trench are located in the immediate vicinity of the earthquake epicenters, a warning via the warning centre in Jakarta is not always possible here because of the very short time until the arrival of a tsunami. Here, above all provisions must be made through education and training of the population.
Tsunami buoys (also known as Tsunameter) are no independent WARNING systems! In all tsunami warning systems around the world they are MEASURING instruments for the verification of a tsunami. The most important information, namely the magnitude and fast localisation of an earthquake, without which neither a simulation of the location nor a warning can be produced, CANNOT be delivered by buoy systems.
At the beginning of the project buoy systems were included in the planning, because they belonged to the "classic" instrument pool of the existing tsunami warning systems. The buoys developed within GITEWS belong to the most advanced worldwide. In the course of the project it quickly turned out that the buoy information cannot be on hand in time for the quick warning necessary in Indonesia (5 minutes after the earthquake), however equivalent information can be obtained in the required short time span through the integration of land-based GPS as an innovative element. To at least deliver information within the first ten minutes of an earthquake, the buoys have to be very close to the earthquake zone and thus anchored close to the coast of Indonesia. The possibility of "vandalism" by fishermen who use the buoys to moor their vessels was, however, underestimated, as was the dense ship traffic near the coast.
Oceanographic instruments are particularly expensive to maintain. The cost calculation for the operation and maintenance of the Indonesian system as a whole reveals that the maintenance and operation of the buoy systems alone (20 in total, of which 10 from Germany) costs as much as all of the approximately 280 instruments installed on land. A cost / benefit analysis that takes into account the fact that the buoy data usually comes too late for the first and most important warning and considers the limited availability of the systems due to vandalism and extensive maintenance led to the decision to no longer include the buoy systems for early warning in Indonesia. Due to the development and expansion of novel land-based measuring systems, the offshore buoys are no longer necessary for tsunami early warning in Indonesia.
The buoy systems which were developed as part of GITEWS turned into an independent, innovative measuring system with GPS sensors to verify a tsunami in the open ocean. As such, they may be deployed in the Indian Ocean – in fact, all the world's oceans – as a useful and reliable tool, if operation and maintenance can be assured technically, organizationally and financially.
There is no full protection against natural disasters, which also applies to large tsunami. The shores of the main Indonesian islands are faced with extremely short early warning times of around 30 minutes, for the islands of Sumatra there is practically no advance warning. It is obvious that megacities such as Padang on the southern coast of Sumatra cannot be evacuated in such a time period. The population has to be trained (evacuation) and offered preventive measures with technical infrastructure such as shelters (vertical evacuation facilities near the beach, shelters ...), and emergency plans have to be developed and implemented.
These activities, grouped under the term "capacity development", are an integral part of a sustainable and effective early warning system. Without appropriate preventive measures and effective education and training programs, the best measurement technique is worthless. In Indonesia, this Capacity Development set out with German support already during the GITEWS project.
Scientists, disaster management, national and local government and local people must be trained in what to do during a strong quake and a tsunami warning and what preventive measures can be taken. The earthquake tragedy in Japan in March 2011 has shown how much of a harm reduction effect preventive and training measures may have even with major disasters. In the GITEWS project capacity development activities were established in three test regions (Padang, Sumatra; Cilacap, South Java; Kuta / Sanur, Bali). They were developed with the local authorities and the local population and established as binding. They include the elucidation of the operating mode of the early warning system, the definition of hazard maps as a basis for evacuation plans, evacuation routes and infrastructure planning for the future. Together with the Indonesian partners local communication means (sirens, loudspeakers, police, local radio and TV) were identified, local disaster management organizations (DMOs) were set up and trained and clear mandates in the warning process were defined. Ultimately, the entire sequence of a tsunami warning up to the evacuation of the coastal area was played out and practised. In parallel, the chain of decisions and alerts from the national down to the local level was defined and agreed upon. The project GITEWS has therefore laid the foundation for the national disaster management strategy in Indonesia.
For a sustainable success of the early warning system in Indonesia, this capacity development must now be developed and established more widely. In the near future, the BMBF-funded follow-up project PROTECTS will, together with the newly formed Indonesian disaster management authority BNPB and in cooperation with the Indonesian Academy of Sciences LIPI, distribute the strategies and measures developed in the test regions nationwide.
Moreover, in PROTECTS the scientists and engineers of the warning centre will undergo an intensive and comprehensive training on the warning system, its operation and maintenance.