Biggest California Earthquake of 2012: M6.3 December 14, 2012


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Recent Earthquakes in California

Earthquake activity in California in the 30 days prior to the M6.3 of 14 December. Image credit: USGS

California has been famous for earthquakes, most notably the devastating 1906 event which destroyed large parts of San Francisco.

The USGS historic earthquakes listing includes 13 events of at least M5.0 in the state or its offshore waters between 2000 and 2010.

The largest of these tremors was also an offshore tremor, an M7.2 which occurred off northern California in June 2005.

Small earthquakes are extremely common along the fault zone, as a map of recent seismicity demonstrates.

This earthquake activity is low-level: in fact 2012 has, however, been a relatively quiet year for earthquakes in the state – indeed, the tremor of 14 December followed a period of several weeks without any significant earthquake activity along the western margin of the USA.

California Earthquake Context

To place the event in context: This M6.3 quake was the largest of the year to date, exceeding the M5.6 earthquake which struck the north of California in January. The logarithmic nature of the magnitude scale hides the difference in size: though there’s only 1.1 magnitude difference, today’s California earthquake released almost 45 times as much energy as its predecessor. Today’s quake, however, released almost 175 times less energy than the M7.8 San Francisco earthquake of 1906.


United States Geological Survey. Real time earthquakes map. (2012). Accessed December 14, 2012.

United States Geological Survey. M6.3 SSW of Avalon, California. (2012). Accessed December 14, 2012.

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