The Sunda trench is the region where the Indo-Australian Plate subducts under the Eurasian Plate. The trench runs directly along the coastline off Sumatra (Indonesia). A frequent earthquake activity is one consequence of the subduction. The epicenter of the earthquake on December 26 in 2004 is marked in red.
(Map:
Wissensplattform eskp.de, Licence: CC BY 4.0)
Different technologies are combined to detect a tsunami and to forecast the wave height as well as the run up areas of the tsunami. The grafic illustrates the different sensor systems (earthquake detection, tide gauges, GPS) of the Indian Ocean tsunami early warning system. The sensors and further aspects will be explained in detail on the following pictures.
(Illustration:
GFZ)
Earthquakes are recorded with a seismometer. A tsunami is mostly triggered by an earthquake on the ocean floor, therefore a fast and relaible earthquake detection (location and strength) is essentia.
(Photo:
GFZ)
GPS, a technology also used for navigation systems, allows to measure plate movements. Due to strong earthquakes the mainland can be shifted up to several meters. This offset can be determined by GPS.
(Photo:
GFZ)
Along the coast and on islands of the coast tide gauges are installed to identify unusual sea level changes.
(Photo:
GFZ)
The different sensor data are transmitted via satellite to a central hub. The hub is installed at the roof of the tsunami early warning centre in Jakarta, Indonesia.
(Photo:
GFZ)
In a database, several pre-calculated simulations are stored. Depending on the location and magnitude of the earthquake, a suitable simulation is selected within a few seconds from this database. Since the topography of the ocean floor has a great influence on the wave height and wave velocity, these parameters are also taken into account.
(Map:
AWI)
The wave height and velocity of a tsunami wave is direct correlated with the water depth.
(Illustration:
Wissensplattform eskp.de, Licence: CC BY 4.0)
Earthquake information, GPS data, sea level changings, as well as the results of the simulation/modelling are at hand at the tsunami early warning centre in Jakarta. A decision support system evaluates immediately all the information. A recommendation is given to the officer on duty and he has to decide about publishing a warning message.
(Photo:
GFZ)
The tsunami early waning centre in Jakarta, Indonesia.
(Photo:
A. Helm/GFZ)
The building of the tsunami early warning centre in Jakarta, Indonesia. The warning center is responsible for geophysical and meteorological services in Indonesia.
(Photo:
H. Letz/GFZ)
Numerous trainings were carried out to teach the Indonesian staff the technologies, the sensor systems and the software programs.
(Photo:
H. Letz/GFZ)
Numerous evacuation instructions and maps marking the evacuation routes for the population.
(Photo:
H. Letz/GFZ)
Evacuation exercise with students in Indonesia.
(Photo:
GIZ)