Two major marine surveys off northern Papua New Guinea (PNG) earlier this year now suggest, when survivors' reports are taken into account, that last summer's disastrous tsunami there was caused by a sediment slump 25 km offshore. The slump was probably the result of seabed shaking from an earthquake. Not only was a sediment slump, or submarine landslide, responsible for the tsunami, according to the data, but the magnitude and wave-height distribution of the tsunami along the coast were the result of focusing by local seabed morphology.
The conclusions are based on new off-shore bathymetry, remote operated vehicle (ROV) dive investigations, the time delay between the source earthquake and when the tsunami struck, computer simulation models, and earthquake aftershock distribution. The most critical evidence is in survivors' accounts of the timing of the tsunami relative to the initially felt earthquake and aftershock [see Davies, 1998a].