August 28, 2007

What’s shaking in Santa Monica?

Have no fear, the big one (probably) isn’t in the near future
By Emily Skehan

UNDERGROUND Angelenos, tremble not.

Despite the handful of earthquakes felt here in Santa Monica this summer, and the devastating Peruvian tremblor on Aug. 15, experts say the next “big one” is hardly imminent.

In fact, the Los Angeles region may even be in the midst of a 1,000-year period of relative seismologic complacency.

Still, thoughts of a crumbling earth beneath their feet are never too far from people’s minds.

“We did talk about earthquakes on the plane,” said Tarek Fadlallah, of Bahrain, who is vacationing in Santa Monica along with his family. “It crossed our minds as something that happens here.”

California’s notoriety as an earthquake epicenter is something of which visitors are aware, added Fadlallah, but after experiencing one firsthand, he’ll take his chances.

“I don’t think the big one is going to hit during the two weeks we’re vacationing here,” he said.

In the past month, two earthquakes that registered at 3.5 or above on the Richter scale occurred in Southern California, both near Chatsworth. The stronger of the two quakes, which struck on Aug. 9, caused noticeable shaking in Santa Monica.

The Richter magnitudes are based on a logarithmic scale; for each number you go up on the scale, the amplitude of the earthquake increases tenfold. Earthquakes of about 3.0 to 5.0 can be felt by most people, but tend to cause only minor damages, if any at all.

Santa Monica residents might be understandably on edge about seismic rumbles after the devastation caused by the 1994 Northridge quake. Registering a 6.7 on the Richter scale, the earthquake produced the strongest ground motions ever recorded in an urban setting in North America, and caused the collapse of major freeways, parking structures, office buildings and apartments in and around Santa Monica.

“The tremblors we’ve been having lately have put the local community on high alert,” said John Pacheco, executive director of the Santa Monica Red Cross chapter. “We’ve had a lot of individuals and businesses calling in for CPR and first-aid classes.”

The local ranks of volunteers have swelled since Hurricane Katrina two years ago, Pacheco noted — the Santa Monica chapter has a pool of about 1,000 volunteers, an estimated 250 of which are active and fully prepared to be deployed for a disaster abroad or one here at home.

“In a way, these international disasters and local happenings are good,” said Pacheco, “because they help to heighten consciousness and get people prepared.”

SLEEPING GIANTS

A paper that was released Friday in the September issue of the journal Geology indicates that the Los Angeles region may be in what is known as a “lull” — a period of relatively infrequent and less intense earthquakes.

“What we were doing with this research was looking at how the rest of California interacts with the San Andreas fault line, and with itself,” said David Bowman, associate professor and chair of the Department of Geological Sciences at Cal State Fullerton. Bowman is one of the three co-authors of the paper, along with James Dolan and Charles Sammis of USC.

“The really interesting finding that we had, and what ended up being the focus of the paper, is this idea that the Los Angeles region and the Mojave area tend to take turns in absorbing the most energy and thus having stronger and more frequent earthquakes — controlled by what happens on the San Andreas.”

The two fault zones tend to alternate more activity in approximately 1,000- to 1,500-year intervals — that is, Los Angeles would experience more clustered and intense quakes for one period, and then the Mojave region, according to the researchers.

Los Angeles is currently the region experiencing less activity, they conclude. However, this doesn’t mean that earthquakes are unlikely to occur.

“Even though this is a so-called lull,” said Bowman, “that term is very misleading. We can still have something on the magnitude of the Northridge quake, which was a 6.5.”

“In terms of risk, we have the unusual luck of having all of our faults right beneath us, so even an earthquake that is relatively small and unimportant on the geographical scale can still have devastating consequences here in Los Angeles.”

But when will the lull end? Bowman and his colleagues have no prediction as to when the next big one might hit — it could be anytime between tomorrow and 500 years from now. But when Los Angeles does start absorbing more of the energy from the collision of the Pacific and North Atlantic plates, earthquakes in the region will be something to worry about.

“If we were to come out of this lull, we would start to see earthquakes on longer stretches of faults, or even earthquakes caused by multiple fault lines at once,” said Bowman.

“This could potentially be more like the devastating events we’ve seen in Japan and other parts of the world — magnitudes of 7, 7.5.”

Those types of quakes — which have yet to strike Los Angeles since it became a major city — have occurred in the Mojave region, such as the 1992 earthquake in Landers that hit a 7.3 on the Richter scale, Bowman said.

“The ’92 earthquake was one heck of a ride,” said Bowman, “and Landers doesn’t have skyscrapers.”

SHAKE ON IT

So does this summer’s seismic activity serve as a foreboding sign of what’s to come? Experts and local residents think not.

“There have always been these little earthquakes,” said ex-Angeleno Stephanie Cooley, who now resides in Oregon. “I remember them even as a kid.”

After having gotten used to the idea of earthquakes while growing up in Southern California, Cooley thinks the small shakes might even be a good sign.

“It’s more of a relief than anything,” she said, “I think if you have smaller ones it’s less likely for a big earthquake to occur.”

San Francisco resident Patricia Brown isn’t overly concerned either.

“You just don’t live your life in fear, thinking about it all the time” she said.

Seismic authorities agree that there’s no use in panicking about the next big quake.

“Actually, seismic activity is pretty quiet right now,” said Kate Hutton, a staff seismologist at Caltech who has been dubbed “The earthquake lady.”

“It’s sort of like the weather — some years, it’s dry, and others, there’s a lot of rain. We’ve had a few tremblors this summer, but it’s fairly low relative to the average.”

Bowman pointed out that for every decrease in magnitude, the number of earthquakes increase greatly. That is, earthquakes that measure lower on the Richter scale occur on an exponentially more frequent basis.

Other experts confirm that predicting a “big one” is a waste of time.

“The problem with these lulls and periods of heightened activity is that they’re not regular; they don’t have any predictive value,” said Doug Gizen, a geophysicist with the United States Geological Survey.

“It’s kind of like a craps table; sometimes it runs hot and sometimes it runs cold. If you’re trying to make money that way you’re probably disappointed.”

Indeed, while Bowman and his colleagues are fully aware of the impact that a major earthquake could have on Los Angeles, they have greater concerns on their minds.

“You’re much better off paying attention to which way the cars are coming when you’re crossing the street,” said Bowman. “That’s a greater danger in Santa Monica.”

SHAKE HAPPENS

Despite the lack of crystal ball clarity in forecasting the next dangerous shake, Californians are advised to prepare for the worst when fault lines get active.

“People in this state should generally not forget that they live in an earthquake area,” said Hutton.” They should expect an earthquake to happen any time, keeping aware of their plan and making sure their kit is up to date.”

Having a list of emergency contacts, an updated earthquake kit, and a detailed plan of how their family is going to find shelter and communicate with each other are all important ways to stay ready.

“When there is a large, particularly dangerous earthquake, people are reminded that they live in an especially dangerous area,” said Gizen.

“As the years go by, your food goes bad, your water goes stale, your batteries die ... and then the big earthquake happens.”