T waves from the 1998 Papua New Guinea earthquake and its aftershocks: Timing the Tsunamigenic slump

Emile A. Okal*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

T waves recorded at hydrophone and seismic stations following the Papua New Guinea earthquake of 17 July 1998 and its aftershocks show that a small event at 09:02 GMT featured source properties incompatible with an elastic dislocation of appropriate body-wave magnitude (mb = 4.4). These include an exceptional duration (47 s at the Wake Island hydrophone station WK31), a spectrum rich in high frequencies (7 to 12 Hz), and a generally low spectral amplitude. These characteristics can be explained by the model of an underwater slump, accelerating from a standstill and eventually slowing down. The relocation of the 09:02 event is compatible with its location within an amphitheater inside which shipboard cruises in 1998 and 1999 documented the presence of a 4 - km3 geologically fresh slump. We propose that the slump took place at 09:02 on 17 July 1998, i.e., 13 minutes after the mainshock, and that it generated the locally catastrophic tsunami, whose properties (amplitude and distribution of runup; timing) could not be explained by a dislocation model.

Original languageEnglish (US)
Pages (from-to)1843-1863
Number of pages21
JournalPure and Applied Geophysics
Volume160
Issue number10-11
DOIs
StatePublished - Oct 1 2003

Keywords

  • Landslides
  • T waves
  • Tsunamis

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

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