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Increased quake activity predicted for California faults

There is growing concern among seismologists that the 7.2 Mexicali earthquake April 4 placed more pressure on Southern California's faults, resulting in increased quake activity over the last three months.

The latest evidence was Wednesday's magnitude 5.4 Collins Valley earthquake that rolled from the mountains south of Palm Springs, leaving no major damage but rattling nerves throughout the region.

Wednesday’s quake was centered in the San Jacinto fault zone -- Southern California’s most active -- which runs 100 miles from the border northwesterly toward Riverside and San Bernardino.

Scientists had warned for some time that the Mexicali quake had transferred pressure from the Mexican border area toward the San Jacinto fault and nearby Elsinore fault – which runs 110 miles and could cause major damage in urban areas -- making quakes there more likely.

 “The probability of a larger earthquake on those faults could be high within the next year or two,” said John Rundle, a physics and geology professor at UC Davis.

Rundle said the aftermath of the Mexicali quake is turning out to be significantly different than the aftermath of the two other large quakes to hit Southern California in the last two decades.

Both the 7.3 Landers quake in 1992 and the 7.1 Hector Mine quake in 1999 in the Mojave Desert resulted in aftershocks that dissipated relatively quickly. By contrast, the Mexicali quake has been followed by aftershocks and “triggered earthquakes” that are showing no signs of ending.

 “This thing seems to be popping off with lots of small earthquakes, and it’s not decaying very quickly … which to me is worrisome, frankly,” he said.

Experts are particularly concerned because the northern edges of the Elsinore and San Jacinto fault zones line up, respectively, near the Whittier fault, which runs into Orange and Los Angeles counties, and the San Andreas fault. Both faults could produce catastrophic quakes.

Smaller earthquakes continue at an unexpectedly high level far north of the Mexicali quake in the Inland Empire.

“Under normal circumstances, you have a rather rapid die-off of activity after an earthquake. But in this case, the activity seems to be motoring along at a fairly high level,” Rundle said.

In contrast, Rundle’s analysis shows the probability of a large earthquake -- such as a magnitude 7 -- has decreased closer to the Mexicali quake area, such as near San Diego.

Rundle is involved in research that is looking to take patterns of smaller earthquakes that have occurred after the Mexicali earthquake and using them to forecast probabilities of where larger earthquakes will be.

“You can actually mathematically map the transfer of stress from one fault to another after an earthquake,” Rundle said. “Small earthquakes are a response to the underlying levels of stress. The higher the level of stress, the higher number of small earthquakes one typically finds. We use the patterns of small earthquakes to forecast the occurrence of larger earthquakes.”

Another piece of evidence are science stations that are built on both sides of the earthquake faults. Satellite imagery of those stations show that both sides of the faults are increasingly moving past each other, indicating growing strain.

Andrea Donnellan, a Jet Propulsion Laboratory geophysicist, likened the Mexicali quake to the initial crack in a car’s windshield.

“Over time … it cracks more,” she said. “The cracked head is where the stress is highest, and that will propagate.”

Increased strain on a fault, Donnellan said, looks like a rubber band that is increasingly stretched.

“Stretch it for a while, it will break,” she said.

The observations underscore that earthquake faults need to be looked at as a system -- similar to how weather patterns in Alaska and on the other side of the Pacific Ocean can affect California.

“You can’t look at it in a vacuum. If you look at it from a system perspective where all these faults interact with each other … you can get an idea how a fault can turn on or off an earthquake on another fault,” Donnellan said.

-- Rong-Gong Lin II

 
Comments () | Archives (19)

Just another reminder to keep your earthquake kit updated and ready.

I have been following these California earthquakes for several months (earthquakes in general for decades). I find this article an urgent one, a must read. The last thing the United States needs is another major national disaster, and California is in no shape to handle this with huge cuts in First Responders; and a lack of money - emergency funds. Nor do I have any idea of the state of California hospitals to handle a major trauma?

We currently have an enormous amount of data manipulation on earthquakes and we don't seem to use it that much. Not too long ago, there was no such thing as an earthquake log with exact lat/lon, time or date. We can use the data to cross-compare, they don't seem differ much from the ripple effect a stone dropped in water makes.
Example the Easter Sunday earthquake. It took 9 weeks for that force to impress another fault and create another earthquake about 50 miles N. The second one it took only 3 weeks to create a third big one, again about 50 miles to the N. Why only a third of that time? Probably because the faults are much denser closer to Los Angeles area compared to the area at the border with Mexico. That last earthquake was on 7/7/10, if this continues are we looking at another one on 7/14/10?

Personally, my brother is a geophysicist at the Un. of Hawaii, and has studied the California fault system for years. I asked him once if the rumors were true, that pieces of CA could actually break off and go into the water. He smiled. Then he simply said "yes, but not could, will."

A good 8 + shaker would bring a lot of emergency funding to southern California...Shake-Baby-Shake!

Nothing we can do about a possible large Earthquake but hope to be prepared and hopefully not taking a shower at the time, I pray. Yes, 'Pray' we must all pray that we'll all stay safe wherever we might be when one hits at any time. As scary as it is, if we were to know when one would hit there would still be nothing we could do anyway.
My cupboards are full with food, I've got 5 five gallons of water stored for emergency, flashlights, batteries, a wrench to turn off the gas if needed, and a first aid supply that hopefully will do. Most likely I'll want to run outside if I can, but that can be dangerous too. Don't know until it happens. Be safe all of you and Pray for California to survive. Wow, just a thought about the year 2012 they say will be the end of the civilization, since they're predicting 1-2 years for a big one, hope not. This is scary!

As nerve-wracking as earthquakes are, here's something to keep it all in perspective:

Compared to the earthquakes in California, substantially more damage and destruction, plus human deaths, are caused in the Midwest by... get this... Winter.

Winter: The Destroyer of Man.

We've been listening to the same predictions for how many years?

I'll be having a cocktail on my patio, thanks.

I know this may sound a little paranoid, but has any one else put two and two together as to all the earthquakes around the globe recently and come up with anything to do with the Hadron Collider...or am I just paranoid. I didn't think I was, now or before. Is anyone looking into that? If so, can you enlighten us. Its a tad of a coincidence that they are happening on opposite sides of the globe at the similar times.
Will it all end in 2012, well no more than it was going to end at midnight
December 1999, going into January 1st,2000! That didn't happen did it. Of course not. All this stuff is there to scare you, no matter how long ago it was written, fear not.

Sounds like the prophesies may be true?

Relax everyone. These seismologists are just guessing and making random forecasts without ANY real scientific fact. There is just as much probability that the Mexicali quake decreased stress in the Calif faults as there is probability that the stress increased. The faults in CA are a complex web. Most likely some faults realized increased stress while others decreased. Don't believe everything that these fancy college professors say because if they really knew what they were talking about they'd have a real job in private companies instead of government jobs.

Five gallons per person may be enough water, but don't take chances. And change the water from time to time. Have enough food and water for at least two weeks, and have extra food for people who will drop by, because they will. Make sure you have many plastic bags to use in your toilet. I hope you have a back yard to store them. Think about everything you do all week, and figure out a substitute, and store it where it will be getable after an earthquake. I have.

Here in the Bay Area, we think the Hayward Fault will go next. That is the major East Bay fault. Historically, when the San Andreas breaks, the Hayward fault breaks shortly there after. But it hasn't. There is a third fault, the Calaveras that is do to break that is likely to go. So we are just waiting.

Most people are in denial, because they can't face it. All you can do is get your house, or the building you live in as save as you can, and get as ready as you can for the next big one, because it is coming, and maybe in your life time.

First of all, in response to those who believe that CA or peices of CA will "fall off into the ocean"... please do a little more research than "my brother at a university". The largest of earthquakes will not drop CA off into the ocean. CA is NOT an Island! The most that would happen is that CA will rotate counter-clockwise up the coast and become part of Oregon. (in about 10,000 years) Look at the Pacific plate on the USGS website and notice that it is rotating counter-clockwise causing all of these earthquakes (ring of fire quakes). For CA to fall off into the ocean, it would have to be floating. It is not. Fortunately, most of CA is already "earthquake prepared" (buildings and structures) so damage from a large quake will not be at a "national emergency" level. IMHO.
Peace!

So, now scientists are claiming that earthquakes are a mother earth's warning that James Cameron is about to produce another over budget stinker?

What we need is some type of megadisaster that only kills politicians, lawyers, investment bankers, meth freaks and crackheads. Just one of those babies and we'd be right back on top. Just sayin'.

Relax: Yes, some faults did experience a decrease in stress. But from a standpoint of hazard and preparedness, don't you think it makes sense to focus on the faults that had an /increase/ in stress? You know, the ones more likely to cause a large damaging earthquake nearer in the future?
Seismologists admit openly that we cannot predict earthquakes. At no point here has anyone issued a prediction. But based on those stress transfer calculations - which have proven quite robust in the past (see: Joshua Tree-Landers-Big Bear-Hector Mine) - none of the earthquakes that have occurred in Southern California after the 4 April Mexicali event have been in surprising places.
Lastly, most of the organizations that do the groundbreaking research on the earthquake process and seismic hazard are universities and government groups. They have the resources and the funding to promote intensive field research, computer modeling, data analysis, and probability calculation. That kind of work doesn't tend to occur so much within private companies. The private groups may send a geologist out to a building site to find a fault, and that's all well and good, but its in the universities and the USGS that work on understanding these faults is being done. Do not devalue these people.


Gheorghe: It probably has more to do with the stress states on the individual faults /before/ the Mexicali event. Though faults that are closer to each other do influence each other more strongly. Given that there's no way to know that pre-event stress state - only how much the stress changed due to the big quake - there's no way to say when exactly any fault will go off, no matter how strong the stress perturbation.


Melissa: California is not going to fall into the ocean. I don't know any geophysicist who would tell you that this urban legend is true. Part of it will detach and slide along itself and end up slamming into Alaska (after a period of Los Angeles and San Francisco being next to each other), but it won't fall in. Hawai'i, however...chunks of the islands periodically fall off and cause huge tsunami. USGS puts out a really good poster showing bathymetric images of older Hawai'ian landslides.

All those illegal alien Chicano gang bangers are present to rush to assist their fellow citizens and to assist in the rebuilding of civilization.

It really sucks that Mother Nature could be so mean. She gives us earthquakes, floods, hurricanes, tornadoes and lightning strikes that either kill people or set off wild brushfires. Even after 200,000 years of human evolution, Man still hasn't invented devices that could be used to fight off Mother Nature's dark side.

Melissa, we have no way of knowing for sure if your brother is a geophysicist at the University of Hawaii or if you even have a brother. I could come on here and say I'm one of the Jonas Brothers or I'm Justin Bieber's older brother. If you do have a brother that actually said what you claim he said, then the University of Hawaii owes itself to terminate his employment there. It is reckless and irresponsible of you and your brother to put out false alarmist predictions with the intent of creating unnecessary panic. That's the problem with allowing anonymity on the Internet.


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