The slump origin of the 1998 Papua New Guinea Tsunami

TLDR

The 1998 Papua New Guinea tsunami, which killed over 2100 people, remains controversial because conventional earthquake models cannot explain its extreme run‑up, and submarine mass‑failure tsunamis have been considered rare and largely ignored in hazard assessments. High‑resolution seismic reflection data, T‑phase hydrophone records, and hydrodynamic modeling, combined with geological evidence, were used to image a large underwater slump and reproduce the tsunami’s amplitude and timing. The integrated seismic, hydrophone, and modeling evidence demonstrates that a large submarine slump generated the tsunami, reproducing its observed amplitude and timing and confirming the slump hypothesis.

Abstract

The origin of the Papua New Guinea tsunami that killed over 2100 people on 17 July 1998 has remained controversial, as dislocation sources based on the parent earthquake fail to model its extreme run–up amplitude. The generation of tsunamis by submarine mass failure had been considered a rare phenomenon which had aroused virtually no attention in terms of tsunami hazard mitigation. We report on recently acquired high–resolution seismic reflection data which yield new images of a large underwater slump, coincident with photographic and bathymetric evidence of the same feature, suspected of having generated the tsunami. T–phase records from an unblocked hydrophone at Wake Island provide new evidence for the timing of the slump. By merging geological data with hydrodynamic modelling, we reproduce the observed tsunami amplitude and timing in a manner consistent with eyewitness accounts. Submarine mass failure is predicted based on fundamental geological and geotechnical information.