On September 28, an earthquake with a magnitude of 7.5 occurred on the Indonesian peninsula of Sulawesi, in a depth of ten kilometers. The quake triggered a local tsunami, although the location of the epicenter, the tremor and the quake were atypical for triggering such a tsunami event.

The Indonesian tsunami early warning system, which was set up by an international consortium led by GFZ German Research Centre for Geosciences after the devastating tsunami of Christmas 2004, reported a tsunami alert with heights between 0.5 and 5 meters five minutes after the earthquake on 28 September.

This alert was distributed through the usual communication channels in the region at risk, i.e. to the state disaster management agency BNPB, local authorities as well as TV and radio stations.

According to current knowledge, this warning was canceled about half an hour later by the staff of the Warning Center.

Five minutes after the earthquake the tsunami warning was set while twenty minutes passed until the actual arrival of the wave, according to statements of the State Geological and Meteorological Service BMKG.

Whether and how the warning from Jakarta arrived in Palu is still unclear. From GFZ’s point of view, the early warning system worked technically. Any gaps in the transmission of the warning are yet to be clarified. (jz)

More information on the Early Warning System