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O.C. might face increased threat from San Andreas fault
January 25th, 2009, 12:59 pm · 13 Comments · posted by Gary Robbins, science writer-editor
On-going research by UC Irvine says the mighty San Andreas fault breaks more often than scientists thought, which could mean there’s an increased risk the system will produce an earthquake large enough to cause widespread destruction in Orange County.
Geologist Lisa Grant Ludwig says in an upcoming journal article that the San Andreas– which runs from the southern Mojave Desert to the Bay area — generates a big quake, on average, every 137 years. That’s more than 60 years more often than some previous estimates.
Ludwig’s estimate is based on radiocarbon analysis she’s been doing on the Carrizo Plain section of the fault, which is located in San Luis Obispo County, about 140 miles northwest of Orange County. She looked at the recurrence time of quakes, dating back to roughly the year 1210. The analysis she’s about to publish is a refinement of data she publicaly presented in August 2008, when she said in an online abstract:
“These chronological data imply that the Carrizo section fails more regularly than previously thought and may be ready to rupture, though the data are not sufficient to forecast its magnitude.”
CLICK IMAGE to enlarge.
The San Andreas last produced an immense quake in January 1857 when a magnitude 7.9 shaker erupted 45 miles northeast of San Luis Obispo. The so-called Ft. Tejon quake caused about 30 feet of surface displacement in the Carrizo Plain and it shook large sections of Southern California hard, the USGS says. Seismologistsfear that a new quake in that region could cause the southern leg of the San Andreas to rupture, releasing energy that could kill hundreds of people in Orange County and inflict enormous damage.
The Ft. Tejon event occurred 152 years ago, or 15 years longer than the 137 year recurrence rate cited by Grant. But that rate is only an estimate,and seismologists cannot accurately forecast quakes. And the San Jacinto fault, which cuts through parts of the Inland Empire, may actually pose a greater threat to Orange County because its much closer, seismologists say. (Ready story).
Related stories and information …
- Real-time earthquake list for Southern California
- NEW: 2.2 microquake occurs off coast of Laguna Beach
- Parts of O.C. feel 3.4 quake that breaks along Venice Beach Boardwalk
- January 2009 map of Southern California earthquakes
- O.C. fault produced biggest SoCal quake of 2008
- Animation shows how big San Andreas qauke might shake O.C.
Did you miss …
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I live somewhat close to that monster. I don’t think we are prepared in the South-land for a 7.0+ quake from it.
We have been through 3 presidents, the entire computer generation, and a trillion style and music fads all while waiting for the “big one.” If I based my existence on the “prediction” of the big one, the last 20 years of my life would have been spent in fear.
It will come when it comes. Trends cannot predict the future. We get it, we are WAYYYY past the statistical date for the big one, but it hasn’t come and I think we all just need to be prepaired but not live in fear of it because it will happen, maybe not this week, this year, or this decade, but eventually. We don’t need to sit around waiting for it though.
DAY AFTER DAY
(Tommy Reynolds / Stuart Margolin / Jerry Riopelle)
Shango
Day after day, more people come to L.A.
Ssh! Don’t you tell anybody the whole place is slipping away.
Where can we go when there’s no San Francisco?
Ssh! Better get ready to tie up the boat in Idaho.
Do you know the swim? You better learn quick, Jim.
Those who don’t know how to swim, better sing the hymn.
Tuna at the bowl. Fine fillet o’ much soul.
Whoo! Whoo! What can we do with a bushel of wet gold?
Day after day, more people come to L.A.
Ssh! Don’t you tell anybody the whole place is slipping away.
Where can we go when there’s no San Francisco?
Ssh! Better get ready to tie up the boat in Idaho.
Where can we go when there’s no San Diego?
Ssh! Better get ready to tie up the boat in Idaho.
Do you know the swim? You better learn quick, Jim.
Those who don’t know how to swim, better sing the hymn.
Tuna at the bowl. Fine fillet o’ much soul.
Whoo! Whoo! What can we do with a bushel of wet gold?
Day after day, more people come to L.A.
Ssh! Don’t you tell anybody the whole place is slipping away.
Where can we go when there’s no San Francisco?
Ssh! Better get ready to tie up the boat in Idaho.
Better get ready to tie up the boat in Idaho
To Mario: That’s a gross misreading of the Shango song, which riffed on doomsday predictions. The blog item is a simple summary of new seismic research.
A good time once again to reconsider keeping the El Toro runways for disaster relief purposes considering how they are the ONLY runways in Orange County that are devoid of liquefaction per the State of California Department of Mining & Geology. We will need El Toro’s 10,000′ runways to bring in needed relief supplies and other equipment. If we allow these runways to be demolished just to favor Irvine, what about the rest of us in Orange County when the big one hits, and we have no runways to bring in help?
Has anyone thought to look into the possibility that maybe the earth is ending it’s settling period? What I mean is as the weather cools the wood in a house creaks as it settles. What if the earth is the same and that is what earthquakes and eruptions are. But as the earth gets older settles less and less.
the reason we have earth quakes is due to the movement of tetonic plates for the most part. as long as there is still a hot molten core underneath us the plates will always be moving and shifting creating new continental maps in the span of millions, sometimes hundreds of millions of years . the quakes usually become less frequent when the fualts are in a point of stress. the two plates can be in a state where almost stuck and creating pressure and a fault rupture could be very severe
Lets all hope and pray that I’m on vacation somewhere out of state when it happens.
This is not the end of the earth as someone stated. Just be prepared - water, canned food, TP, a bucket and pet food…if you have a pet.. If you can’t stand the earth shaking, then maybe you should not be liviing here.
Ed Denial dude. Why do you think it is called the pacific ring of fire? We are sitting on a tectonic conveyor belt.
It is not if, but when
Thanks for your cheery thoughts this beautiful Monday morning.
Cynical Says:
January 26th, 2009 at 7:19 am
Thanks for your cheery thoughts this beautiful Monday morning.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
My thoughts exactly……
Ed demonstrates the general misunderstanding of seismology by many people. The concept that we are way past due for the big one is not true. The frequency of earthquakes, or the reoccurrence interval as used in the business, is a very difficult parameter to estimate. Geologists are given relatively little data to go by when developing reoccurrence intervals. Less data means less accurate predictions. Also, Mother Nature is fickle. Just because the statistics say its time to move doesn’t mean it happens on time. There’s a lot of “pluses and minuses” in the actual occurrence intervals. Some times they occur back to back and sometimes long periods of time pass between. The new “average” occurrence interval according to Ms Ludwig is apparently going to suggest 137 years, 60 years different than previous estimates. 60 years is about 80% greater than the previous estimate! Consider this statement from G Jacoby, et al. (1988 ) about the San Andreas Fault, “The discovery that at least 12 kilometers of the Mojave segment of the San Andreas fault ruptured in 1812, only 44 years before the great January 1857 rupture, demonstrates that intervals between large earthquakes on this part of the fault are highly variable. This variability increases the uncertainty of forecasting destructive earthquakes on the basis of past behavior and accentuates the need for a more fundamental knowledge of San Andreas fault dynamics.” So bottom line is the big one IS coming. Where and when it happens may be estimated with considerable error. But Mother Nature is in no big hurry and she will get around to it, some day. Please be prepared.