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

  • Emile A. OkalEmail author


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 (\(M_{\text {PAS}} \,=\,8.1\)), 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.


Tsunami Andaman Islands historical earthquakes 



We are grateful to Ian Saunders (Pretoria), Bernard Dost (De Bilt) and Brian Ferris (Lower Hutt) for access to the excellent seismological archives at their respective facilities. Some figures were drawn using the GMT software (Wessel and Smith 1991). The paper benefited from the constructive comments of two anonymous reviewers.


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Earth and Planetary SciencesNorthwestern UniversityEvanstonUSA

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