Large, pre-digital earthquakes of the Bonin-Mariana subduction zone, 1930-1974

Emile A. Okal*, Dominique Reymond, Sutatcha Hongsresawat

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

9 Scopus citations


The Bonin-Mariana subduction zone is the end-member example of a decoupled system, as described by Uyeda and Kanamori (1979), with no interplate thrust solutions of moments greater than 8×1025dyncm known in the CMT catalog, although a number of earthquakes are reported with assigned magnitudes around or above 7, both during the WWSSN period and the historical pre-1962 era. We present a systematic study of these events, including relocation and inversion of moment tensors. We obtain 15 new moment tensor solutions, featuring a wide variety of focal mechanisms both in the fore-arc and the outer rise, and most importantly a shallow-dipping interplate thrust mechanism with a moment of 4×1027dyncm for the event of 28 December 1940 at a location 175km East of Pagan. Our results show that the modern CMT catalog still undersamples the seismicity of the Mariana arc, which is thus not immune to relatively large, albeit rare, interplate thrust events, with moments 40 times that of the largest Global-CMT solution. Frequency-magnitude relations would then suggest a return time of 320years for a magnitude 8 interplate thrust faulting earthquake in the Bonin-Mariana system.

Original languageEnglish (US)
Pages (from-to)1-14
Number of pages14
StatePublished - Feb 26 2013


  • Bonin Islands
  • Decoupled subduction zones
  • Historical earthquakes
  • Mariana Islands

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes


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