Intraplate seismicity of the Pacific Basin, 1913-1988

Michael E. Wysession*, Emile A. Okal, Kristin L. Miller

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

73 Scopus citations


We establish here a comprehensive database of intraplate seismicity in the Pacific Basin. Relocation and analysis of 894 earthquakes yield 403 reliable intraplate earthquakes during 1913-1988. These numbers do not include earthquake swarms, which account for another 838 events. Most of the remainder (304 events) are actually plate boundary earthquakes that have been erroneously located in intraplate regions. A significant number occur in recent years when location capabilities should have guarded against this situation. Relocations involve a careful linear inversion of P and S arrivals, accompanied by a Monte Carlo statistical analysis. We have also attentively removed the high number of clerical errors and nuclear tests that exist in epicenter bulletins. A geographical examination of the relocated epicenters reveals several striking features. There are three NW-SE lineaments north of the Fiji Plateau and in Micronesia; diffuse seismicity and incompatible focal mechanisms argue against the southernmost, discussed by Okalet al. (1986) and Kroenke and Walker (1986), as the simple relocation of the Solomon trench to the North. Besides another striking lineament, along the 130°W meridian, there is also a strong correlation between seismicity and bathymetry in certain parts of the Basin. In the Eastcentral Pacific and Nazca plates there are many epicenters on fracture zones and fossil spreading ridges, and hot spot traces like the Louisville, Nazca and Cocos Ridges also display seismicity.

Original languageEnglish (US)
Pages (from-to)261-359
Number of pages99
JournalPure and Applied Geophysics PAGEOPH
Issue number2
StatePublished - Feb 1 1991


  • historical earthquakes
  • Intraplate seismicity
  • Pacific Basin

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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