Source Properties of the 1998 July 17 Papua New Guinea Tsunami Based on Tide Gauge Records

heidarzadeh, mohammad ; satake, kenji;

We analysed four newly retrieved tide gauge records of the 1998 July 17 Papua New Guinea (PNG) tsunami to study statistical and spectral properties of this tsunami. The four tide gauge records were from Lombrum (PNG), Rabaul (PNG), Malakal Island (Palau) and Yap Island (State of Yap) stations located 600–1450 km from the source. The tsunami registered a maximum trough-to-crest wave height of 3–9 cm at these gauges. Spectral analysis showed two dominant peaks at period bands of 2–4 and 6–20 min with a clear separation at the period
of ∼5 min. We interpreted these peak periods as belonging to the landslide and earthquake sources of the PNG tsunami, respectively. Analysis of the tsunami waveforms revealed 12– 17 min delay in landslide generation compared to the origin time of the main shock. Numerical
simulations including this delay fairly reproduced the observed tide gauge records. This is the first direct evidence of the delayed landslide source of the 1998 PNG tsunami which was previously indirectly estimated from acoustic T-phase records.