June 25, 2006
Southern California At High Earthquake Risk

With Hurricane Katrina people had a couple of days notice that something highly destructive was coming their way. When the big quake comes to SoCal and LA gets wrecked we'll find out about it right when the big ride starts. The last really big SoCal earthquake was in 1690. The San Andreas Fault has been building up unreleased tension for at least 300 years.

A researcher investigating several facets of the San Andreas Fault has produced a new depiction of the earthquake potential of the fault's southern, highly populated section. The new study shows that the fault has been stressed to a level sufficient for the next "big one"—an earthquake of magnitude seven or greater—and the risk of a large earthquake in this region may be increasing faster than researchers had believed, according to Yuri Fialko of Scripps Institution of Oceanography at the University of California, San Diego.

Historical records show that the San Andreas Fault experienced massive earthquakes in 1857 at its central section and in 1906 at its northern segment (the San Francisco earthquake). The southern section of the fault, however, has not seen a similar rupture in at least 300 years.

Although seismologists have not been able to predict when a great earthquake will occur on the southern San Andreas, most believe such an event is inevitable. Fialko has produced the clearest evidence to date of the strain buildup that will ultimately result in a large earthquake along the southern San Andreas Fault, a 100-mile segment that cuts through Palm Springs and a number of other cities in San Bernardino, Riverside and Imperial counties. Such an event would be felt throughout much of Southern California, including densly populated areas of metropolitan Los Angeles and San Diego.

If you are a SoCal resident now might be the time to start thinking about a really extended trip to some other part of the world.

"All these data suggest that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell. It could be tomorrow or it could be 10 years or more from now," said Fialko.

Bonds have maturities measured in decades. Earthquakes are a substantial risk factor. Hey there bond investors, you might want to think twice before buying bonds of SoCal governments.

Fialko found evidence that the southern San Andreas is mostly locked and continues to accumulate significant amounts of strain. He calculated the rate at which the fault is moving and estimated the "fault slip rate," the pace of the plate movement at the fault, at about an inch per year. According to Fialko, this means that during the last 300 dormant years the fault has accumulated approximately six to eight meters of slip "deficit," which will be released in the future big earthquakes. If all inferred deficit is released in a single event, it would result in a magnitude eight earthquake, roughly the size of the 1906 San Francisco earthquake.

"In the earthquake business, the past is a key to understanding the present and by comparing data on the timing of past earthquakes on the fault with what we have measured over the last 10 years, we can say with some certainty that the fault is approaching the end of its loading period," said Fialko.

If the next quake is much bigger than the 1994 Northridge quake then costs could easily run in to the hundreds of billions of dollars.

When it does rupture on the San Andreas, such a quake could be as deadly as the 1994 Northridge quake, which struck on an unsuspected hidden fault now called the Northridge or Pico and killed 51 people, injured 9,000 and caused $44 billion in damages.

If you are in a wood frame house that is not perched precariously on a hillside your odds of getting killed are quite low. But if you are on an elevated roadway or some old high building or downstream of some dogdy old dam filled with water then your risks go up. For myself personally I'm more worried about the economic disruption (e.g. the need for electricity and internet to do work).

Share |      Randall Parker, 2006 June 25 07:37 AM  Dangers Natural Geological

Adam said at June 26, 2006 2:02 AM:

One of my fears with this earthquake is, if it's >8.0, even 8.1, the Diamond Valley Lake's Dam could colapse:

has a good article about it

This would cause 2 major problems, the first being the flood damage, (I live in menifee, it would wipe out my house),

the 2nd being that the Diamond Valley Lake is intended to be our saftey net against earthquakes, holding six months of emergency supplies for the surrounding areas in the Inland Empire, and it contains 260 million gallons of much needed water for Southern California.

RueHaxo said at June 27, 2006 9:26 AM:

As if Southern California isn't a mess already..........

Seismic said at June 27, 2006 10:44 AM:

I guess that is one way to get rid of the illegal alien problem...

Bob said at June 6, 2008 8:16 PM:

Wow, Seismic, millions of lives are at stake here, and YOU'RE GLAD THAT some of Southern California's illegal alien PEOPLE WOULD DIE from the earthquake. That really shows everyone what type of person you are. (Read the fully capitalized words, ignoring the non-fully capitalized words- spells OUT: YOU'RE GLAD THAT PEOPLE WOULD DIE)) Oh and anyone who agrees with him is no better either, and I know many do.

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