Source Reconstruction of the 1969 Western Sulawesi, Indonesia, Earthquake and Tsunami

The island of Sulawesi, Indonesia, is located in a complex and tectonically active region, and has experienced tsunamis in the past. One of the major earthquake and tsunami events was the 23 February 1969 event that struck the Majene region in western Sulawesi Island. Interpretation of the historical accounts revealed that the Mw 7.0 earthquake generated strong intensity up to VIII on the Modified Mercalli Intensity scale. The earthquake was followed by an unusually high tsunami of 4 m that rapidly decayed within 25 km from the highest observation site. Hypocentre and earthquake mechanism analyses confirmed that it was an inland earthquake with a thrust mechanism. Ground motion modelling is able to reproduce the earthquake intensity but earthquake scenarios are unable to reconstruct the tsunami observations. A plausible solution to explain the tsunami report is from a combined scenario of an earthquake and a submarine mass failure of 0.5 km^3 .