A Tsunami (jap. 津 波, harbour wave) is a water wave that is generated by sudden displacement of huge volumes of water. In the majority of cases this displacement is caused by the deformation of the ocean floor during an earthquake. However, also landslides, volcanic eruptions, and - theoretically - also meteorite impacts are possible mechanisms of Tsunami generation. All of this mechanisms have in common, that they can generate seismic waves that travel through the earth with a velocity of several kilometers per second. Contrarily, tsunami waves reach only velocities of several 100 kilometers per hour. After an earthquake at the Sunda Trench - off the coast of Indonesia - seismic waves arrive at the coast in approximately 30-40 seconds, whereas tsunami waves would reach the coast soonest after 20-30 minutes. Therefore, a dense network of seismological stations, that register the seismic signal are a principal component of GITEWS (German Indonesian Tsunami Early Warning System).
The mission of the seismological component is the near-real-time automatic detection of tsunamigenic earthquakes, as well as the determination of their location and magnitude within a few minutes. Because of its expertise in Internet-based near real-time data acquisition, automatic generation of near real-time earthquake alerts and virtual seismological network management the GEOFON-programme of the GFZ-Potsdam was appointed to design and implement the landbased seismic component of GITEWS.
A fast and accurate determination of the earthquake parameters (location, magnitude, source depth) is essential for a fast Tsunami Early Warning System. A compact measuring network shortens, on the one hand, the time for the shock wave to reach the measuring instrument. On the other hand, however, it is extremely difficult to register and to evaluate the signals of strong earthquakes in the near field. New measuring and evaluation procedures were, therefore, developed for GITEWS.
SeisComP3 is the name of the software programme developed by scientists at the GFZ and the Gempa GbR which, within minutes, determines the location and the magnitude of an earthquake. In this way several strong earthquakes and their individual parameters could already be determined within a good two minutes. The entire seismological network in Indonesia currently avails of over 120 stations.
This evaluation software sets new standards worldwide. SeisComP3 is also meanwhile used by other neighbouring states of the Indian Ocean, for example in the Indian Early Warning System. And in addition this software is further applied on the Maldives, in Pakistan, in Thailand and in South Africa with other countries ready to follow.
