Three of the four strongest earthquakes in California (not including those off the coast) in the past 50 years
have occurred between October 15 and October 18. These included events
in the Imperial Valley area (Mw 7.0) on October 15, 1979, the Loma
Prieta (the world series quake in San Francisco) on October 18, 1989 (Ms 7.2)
and the Hector Mine earthquake on October 16, 1999. Interestingly, these
have each occurred with 10-year intervals. The only other earthquake in
California in the past 50 years of Mw>7 occurred on June 28, 1992 near
Landers, in southern California. While no strong earthquakes are expected
at this time in the region, the history of the region is important to
keep in mind.