The Large Andaman Islands Earthquake of 26 June 1941: Why No Significant Tsunami?

Emile A. Okal*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


We present a modern seismological study of the earthquake of 26 June 1941 in the Andaman Islands, the largest pre-2004 event along that section of the India-Burma plate boundary. Despite a large conventional magnitude (MPAS=8.1), it generated at best a mediocre tsunami for which no definitive quantitative reports are available. We show that the 1941 earthquake took place under the Andaman accretionary prism and consisted of a composite event, whose nucleating phase had a strike-slip mechanism incompatible with a data set of spectral amplitudes of mantle Rayleigh and Love waves. Combining this initial phase with a larger normal faulting mechanism can reconcile them with P-wave first motions, reports of subsidence on the eastern coast of the Andaman Islands and the small amplitudes of any putative tsunami. The small tsunami results from a combination of that mechanism and of a source located under the islands themselves and in shallow water, implying a reduction in amplitude under Green’s law when transitioning to a deeper basin.

Original languageEnglish (US)
Pages (from-to)2869-2886
Number of pages18
JournalPure and Applied Geophysics
Issue number7
StatePublished - Jul 1 2019


  • Andaman Islands
  • Tsunami
  • historical earthquakes

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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