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San Andreas fault capable of magnitude 8.1 earthquake over 340-mile swath of California, researchers say [Updated]

San andreas The "Big One" on the San Andreas fault just got a little bigger.

New research showing a section of the fault is long overdue for a major earthquake has some scientists saying that the fault is capable of a magnitude 8.1 earthquake that could run 340 miles from Monterey County to the Salton Sea. 

Whether such a quake would happen in our lifetime had been a subject of hot debate among scientists. That's because experts had believed that a major section of the southern San Andreas, which runs through the Carrizo Plain 100 miles northwest of Los Angeles, would remain dormant for at least another century.

But that rosy hypothesis seemed to be shattered by a recent report in the journal Geology, which said that even that section of the San Andreas is far overdue for the "Big One." [Updated, Oct. 9: The report, published in August, was written by Sinan Akciz and Lisa Grant Ludwig of UC Irvine, and J. Ramon Arrowsmith and Olaf Zielke of Arizona State University.]

Now, according to U.S. Geological Survey seismologist Lucy Jones, it is entirely possible that all 340 miles of the southern San Andreas could be ready to erupt at any time. Such a scenario would trigger a magnitude 8.1 earthquake, said Thomas Jordan, director of the Southern California Earthquake Center, a calculation with which Jones agreed.

"All of it has plenty enough stress for it to be ready to go," Jones said. "The biggest implication of [the report] is that it increases the likelihood that when we do have a big earthquake, it will grow into the 'wall-to-wall' rupture."

[Updated, Oct. 9: Such a temblor could cause much more damage because with a longer stretch of the fault rupturing, a larger area is exposed to the quake, and the shaking would last longer.]

The walls Jones is referring to are the boundaries of the southern San Andreas, which begins in the Salton Sea and ends in the town of Parkfield in Monterey County. Scientists consider the southern San Andreas fault as one segment generally because it behaves the same -- it rarely rumbles, but when awakened, the shaking can be devastating.

In contrast, the section of the San Andreas north of Parkfield up to Hollister in San Benito County behaves differently. That section constantly moves at a creep -- meaning stress is relieved regularly, so large quakes don't occur there.

Large quakes haven't occurred anywhere on the southern San Andreas for more than a century, making it a sleeping giant that has been building stress for so long it could snap at any moment.

"My concern is that we will get a series of large earthquakes along the San Andreas fault," Jordan said. The last "Big One" to rip through Southern California occurred in 1857, when an estimated magnitude-7.9-quake, ruptured 200 miles of fault between Monterey and San Bernardino counties. It wasn't a wall-to-wall quake: It stopped near the Cajon Pass, near the present-day 15 Freeway, probably because the fault south of it shook just a few decades earlier, in 1812, Jones said. Because the 1812 quake had relieved tectonic tension in that area, it effectively put a brake to the 1857 quake from moving further south.

But with the San Bernardino County section of the fault now having accumulated two centuries' worth of strain, there may not be any brakes now. "Can I imagine the 1857 earthquake happening again and stopping at the Cajon Pass? Probably not," Jones said. "Once you have a big slip, you're more likely to move along down the fault," Jones said. "If the rupture has been made ... that’s a lot of momentum that will keep the rupture moving down the fault."

The San Andreas has long been considered one of the most dangerous faults in Southern California because of its length. Not only do longer faults produce bigger quakes, they emit a type of shaking energy that can travel longer distances.

"So a much larger area is affected by a really large earthquake," Jones said.

In 2008, seismologists developed a scenario for a large earthquake on the San Andreas -- a magnitude 7.8 shaker that begins at the Salton Sea and barrels northwest along the fault toward San Bernardino and Los Angeles counties.

-- Rong-Gong Lin II

Photo: Quake researchers study a portion of the San Andreas fault. Ricardo DeAratanha / Los Angeles Times; Map: U.S. Geological Survey

Comments () | Archives (46)

An earthquake will do wonders for all of the contractors with no work. We need one....Earth Quake! Earth Quake! Earth Quake!

The state legislature should pass a law prohibiting any quakes above a 6.5 within the borders of California. ;-)

I can't wait until SF and LA break off into the ocean then California can be left with nothing but Fuddruckers and Wendy's drive thrus, what a paradise it will be when those cell pools have fallen into the ocean.

Youth Brigade was right!!!eleventy!!!!

We'll sink with California when it falls into the seeeeeeeeeeea.

And still the USGS won't come clean and admit their lying mistakes.

It's Xmas in LA and everyone is chanting 'let it quake, let it quake, let it quake'.

Everyone better be stored up on life jackets too!! This is judgment on America!!!

There are some Cali haters posting....so sad! I'm happy to enjoy our beautiful weather, exciting lifestyle, great people, restaurants, entertainment and shopping. We have it all! If earthquake worries are enough to keep others away...then more power to doomsday predictors! Just be prepared!!

I live in Mexicali its been almost 2 years with earhtquake activity but the 7.2 last april rigth away you knew it was coming a big one after the big noise the earth make just 15 miles from here.. The noise..The noise dont forget.

I don't know what to do with this information. It really makes me want to commit suicide, because I live in California and am dependent on my family right now. Not everyone died in Chile after their quake. Is the chance of survival and the return to normal life possible?

Goodness, what else can they discover about the fault, that it shoots lasers?

I want to be prepared in whatever ways I can, but these stories are too upsetting for me and I don't know what to do. I don't want to hide my head in the sand, but I literally get ulcers and disturb my loved ones with all my fears when I read this stuff.

From some of the comments, you would think non-Californians wouldn't mind the state being annexed by a seismic hit. Some of the warmest and friendliest people can dismiss and de-personalize by wishing ill on Californians. That's like wishing a series of killer tornados to befall the midwest. The folks on military bases here are prepared for a catastrophic event. They are among those who protect YOUR country.

My family moved to LA in 1961. I was just a little tyke but the newspapers were screaming that the big one was coming since it had been over 100 years since the 1857 Tehachapi monster quake. Now it's been 150 years and way way overdue. This is not a laughing matter. I have a home in San Diego and we have been hit with a 7.2 out of Baja and 1000s of aftershocks. The aftershocks are in many different locations from Nevada to Lake Henshaw. I have never seen anything like it. It is best to be prepared and have food and water and a plan in place because it will happen and it's not a joke.

The reality is that the so called scientist are luckey if they find there car in the parking lot.
Any fool that has an internet connection and whatches the earthquakes ocurring on the government site : iris.gov seismic monitor will realize that the San Andreas fault is part of the ocean ridge system under the ocean and it will rise above sea level in time. These ridges ,incorrectly called mid-ocean ridges have a 40,000 mile circumnavigation footprint.

We the people are like an ant population that moves by trial and error. the scent of the lead ant that finds food leaves a trail that all the ant will follow. Gold in california was the scent.
Like ants we populated the rising ridge system that is southern california circumnavigates the globe looks like the seams on a baseball.

Fact: 99 % of all earthquakes happen over and over again in the same ridge and trench system.
when excessive erosion takes place, as in the massive erosion caused by the moonsoon floods caused the situation in India and Packistan called isostatic rebound takes place and you have earthquakes.

Plate Tetonics is a farce- a non-existant cartoon of too many scientists.

Earthquakes are 99% perdictable : they will occur on the iris.gov site where they previously ocurred. It is that simple.
Haiti is a volcano-not concentrated but spread out over the southern penensula. It will happen again.

I will take an earthquake over a tornado/hurricane Any day

Anyone want to buy my condo is Palm Springs?

Just don`t get 'under' anything! Firemen say people are crushed that way, better to stand against a wall, or lay beside bed, table,couch..
which will take the brunt of a falling roof
/debris. School children are told to get under their desks instead of beside them, big tragic mistake. Standing under a door frame is also not recommended.. firemen say they often find peeps crushed under them as well.

i was drawing hover homes that get early detection of such a quake from the quake centers and for the first time in the worlds history the homes new just what to do they were 25% machine 75% home,all the bells and whistles would start to sound like a car alarm and the homes go into the hover mode,all using alternating electric power from the local utility company,and you would be glad you paid your last months electric bill,they would instantley hover off the groundbuck rogers stuff,way out there in la la land some where.

Anything that crosses the San Andreas is going to shift up to 30 feet. Read about the 1857 quake. The ground even liquefied as far north as Stockton sinking trees. The I-5, I-10, I-15, 14, water, power and rail lines are all going to be shut down for a while and many other freeways in the LA basin are going to be closed. Don't assume you will be able to drive home, plan on walking. Think about it, what are you going to do when you are miles from home and everything is shut down? Have food and water in your car, walking shoes and you may want to tune up your bicycle. Old timers in my town once said that refugees took three days to reach t them after the 1906 quake only 90 miles away.

Watch the USGS latest CA/NV quakes website and you can see the pattern of quakes and the stress that had been building.

Good Luck.

oh! no!

this earthquake will happen. and LA will sink to the bottom

SanAndreas has the probability of producing an 8.1 magnitude EQ. The nuclear power plant in SanDiego for example was constructed to withstand a 7.0 EQ. We have a double disaster waiting to happen. We need to make sure these power plants are seismic retrofitted, rebuild with the lessons being learn from Japan..or taken down if at all possible..

This needs to happen now !

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