Los Angeles Seismograph 7:10 AM EST – Credit ABC TV7
# 6780
Residents in Southern California and the Baja Peninsula were on the receiving end of a significant seismic shock overnight, as a 6.3 temblor struck 160 miles off the coast at 2:36 am (local time).
No tsunami was generated, and no warnings went out from the Pacific Tsunami Warning Center. Light to moderate shaking (Max CDI=V) was reported in San Diego and Ensenada according to the USGS.
There were originally reports of a second 6.1 shock, but that may have been a false reading as it no longer appears on the USGS earthquake feed.
The epicenters of these quakes were well off shore, and not along the famous San Andreas Fault which runs through much of California.
The USGS posted this Tectonic Summary.
The December 14, 2012 M 6.3 earthquake 250 km southwest of Avalon, California occurred as a result of shallow normal faulting within the oceanic lithosphere of the Pacific plate. This event is located some 400-450 km west-southwest of the plate boundary between the Pacific and North America plates – the San Andreas fault system in southern California – and is not associated with that fault system.
Instead, this earthquake represents intraplate faulting along northeast-southwest trending normal faults within the crust of the Pacific plate, just to the west of California’s continental shelf. The causative fault is not known at this time. At the location of this event, the Pacific plate moves to the northwest with respect to the North America plate at a velocity of approximately 54 mm/yr.
While the broad region surrounding the December 14, 2012 event experiences frequent earthquakes along the San Andreas and associated faults in southern California, the area offshore and within 250 km of this earthquake has not hosted any events greater than M 6 over the past 40 years. The largest nearby earthquake was a M 5.1 event 200 km to the northeast in June of 2004, 80 km west of the border between the US and Baja California. A M 3.3 earthquake struck approximately 35 km to the northeast in April 1981, representing the closest event in the USGS earthquake catalog.
While this morning’s wake up calls are unlikely to have caused any significant damage, they are a reminder that much of California (along with much of the world) is seismically active.
In 2010 (see Revised Risk Of `The Big One’ Along San Andreas Fault) scientists using better tools and techniques, determined that big earthquakes occur far more frequently along the San Andreas fault than was previously believed.
Major quakes have occurred – on average – every 88 years along the southern section of this fault line, or three times more frequently than prior estimates.
Which makes southern California long overdue for `the big one’.
Shakeout.org, which promotes yearly earthquake drills and education around the country, has been a leader in earthquake preparedness in California.
And the county of Los Angeles – recognizing the many natural disaster threats that face their residents – has produced an excellent L. A. County Emergency Survival Guide.
Well worth downloading, and using, no matter where you live.
To become better prepared as an individual, family, business owner, or community to deal with these types of disasters, I would invite you visit the following preparedness sites.
FEMA http://www.fema.gov/index.shtm
READY.GOV http://www.ready.gov/
AMERICAN RED CROSS http://www.redcross.org/
And finally, some of my own preparedness articles include:
In An Emergency, Who Has Your Back?
