In the event of a warning, only a few minutes are available for making the decision about whether and where the coastal population should be evacuated, as the potential earthquake zones are close to the Indonesian coastlines. The devastating tsunami of 2004 reached the Indonesian province of Banda Aceh only 15 minutes after the source (the initial event of the quake).
Therefore, a tsunami scenario database has been created in GITEWS with 4,400 sources generated for the Sunda Trench in the source model and the most important values are extracted for each scenario: On the one hand, the relevant quake parameters of magnitude, epicentre and displacement at the GPS locations and on the other hand, values regarding the tsunami propagation, such as maximum wave height, arrival time and virtual tide gauge data. Therefore, in the event of a warning, the measurement data from the sensor systems can be compared with the virtual data of the scenario within seconds and the expected wave height and arrival time along the coast can be determined.
During the first minutes after a tsunamigenic quake, the epicentre and magnitude can be determined. Then, all of the matching scenarios of the simulation are selected in the vicinity of the epicentre. With additional measurement data, particularly from GPS stations, the number of possible scenarios is then limited and those that are most likely will be used for early warning.