9/16/2015, M4.0 Near Big Bear Lake

Last updated September 21st, 2017

  • 16 Sep 2015 09:10:47 PDT, (34.139, -116.857), 13km SSE of Big Bear Lake, CA.
  • Initial magnitude was revised to M4.0 once all data became available and were analyzed.
  • Depth was about 11km (7 miles), and the event was widely felt (out to ~200km) with light to moderate shaking at the epicenter.
  • So far there have been a few small aftershocks: two over M2.0, the first within a few minutes of the M4.0. More may be expected, largest could be M3.0 if the M4.0 is the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • Focal mechanism and moment tensor solutions for the M4.0 show oblique normal motion. It is not possible to say exactly which fault at this time; local geology is complex and several large fault systems converge near this area (San Andreas, Pinto Mountain are within a few miles).
  • Events have occurred in this area historically, since our records began in 1932 we’ve had 22 events of M4 or greater within 10km of today’s event, the last was an M4.6 on 1 Oct 1995, many were aftershocks of the Landers earthquake in 1992.
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