Seasonality of great earthquake occurrence at the northwestern margin of the Philippine Sea plate

Masakazu Ohtake, Hisashi Nakahara

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


A significant seasonality is found in the occurrence time of past great earthquakes (M ≥ 7.9) in the northwestern margin of the Philippine Sea plate. Among the thirteen earthquakes cataloged, five took place in December, and all the earthquakes are included in the seven months from August to February. The probability that such a skewed distribution occurs by chance is as small as 2.0%. This seasonal concentration of earthquakes suggests that a small stress increase may trigger an earthquake when the future focal zone is at a critical condition to release a large rupture. As a candidate factor of the earthquake triggering, we tested a possibility of stress change caused by annual variation of the atmospheric pressure. However, the incremental stress is no larger than 30 Pa, and it hardly accounts for the seasonality of the great earthquakes.

Original languageEnglish
Pages (from-to)689-700
Number of pages12
JournalPure and Applied Geophysics
Issue number2-4
Publication statusPublished - 1999 Jan 1
Externally publishedYes


  • Atmospheric pressure
  • Earthquake triggering
  • Great earthquakes
  • Philippine Sea plate
  • Seasonality

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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