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Revised Risk Of `The Big One’ Along San Andreas Fault

 

 

# 4825

 

 

For years scientists have believed that big earthquakes occur along California’s San Andreas fault on average every 250 to 450 years. 

 

While conceding that another temblor could strike at any time, with the last big quake just 153 years ago , many residents have taken solace in the belief that another quake wasn’t `due’ for another hundred years.

 

Which of course reminds one of the cautionary tale of the statistician who drowned trying to wade across a river that was – on average – only 3 feet deep.

 

This week scientists, using better tools and techniques, have 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’.

 

According to the Los Angeles Times report (below), using carbon dating and LIDAR (Light Detection And Ranging) techniques, scientists have calculated that big quakes occurred sometime around the years 1417, 1462, 1565, 1614, and 1713.

 

As you might imagine, the release of this data has spurred a fair amount of media coverage this weekend, including:

Study shakes up scientists' view of San Andreas earthquake risk – Los Angeles Times

California Overdue for 'the Big One,' Geologists Say – Fox News

L.A. 'Big One' could come sooner than expected: study - AFP

 

The journal Geology has the paper, detailing these findings, and the abstract is available online.

Century-long average time intervals between earthquake ruptures of the San Andreas fault in the Carrizo Plain, California

Sinan O. Akçiz, Lisa Grant Ludwig, J Ramon Arrowsmith and Olaf Zielke

 

 

The `good news’ in this study is that the next big earthquake won’t necessarily be as massive in size or strength as the 1857 quake.  But scientists concede that the San Andreas is capable of producing up to an 8.1 magnitude event.

 

 

Which makes this year’s National Preparedness Month (NPM10), due to kick off in a little over a week, all the more important for those who live in southern California.

 

From the USGS Great Southern California Shakeout website,  we’ve this 4 and 1/2 minute video called Preparedness Now (Streaming | Video) that  “depicts the realistic outcome of a hypothetical, but plausible, magnitude 7.8 earthquake on the San Andreas fault in Southern California.”

image

 

Visit the Shakeout site (above) for more information on how you can participate in this yearly exercise.

 

For more on earthquake and general disaster preparedness, you might wish to look at these essays as well.

 

The L. A. County Emergency Survival Guide
An Appropriate Level Of Preparedness
FEMA Asks: Are You Earthquake Prepared?
Inside My Bug Out Bag
Red Cross Unveils `Do More Than Cross Your Fingers’ Campaign

 

And of course, Ready.gov  and FEMA are great resources for earthquake, and general, disaster preparedness information.

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