NR 2006-08
April 4, 2006

Contact: Ed Wilson
Mark Oldfield
Don Drysdale
(916) 323-1886


When Dr. Michael Reichle, chief seismologist for the Department of Conservation’s California Geological Survey (CGS), meets non-scientists for the first time, the conversation is almost a given.

“The first thing people say to me when they find out I’m a seismologist is `You’ll tell me when the big one’s coming, won’t you?’ ” Reichle said. “I usually tell them, `There’s a good chance you’ll know before I do.’ ”

The public has many misconceptions about earthquakes – whether it’s the inevitability of California falling into the ocean or the wisdom of standing in a doorway during heavy shaking -- and about science’s ability to predict them. As the April 18 centennial of the 1906 San Francisco earthquake approaches, CGS hopes to debunk some common quake myths and help the public become better informed about the potential hazard.

Take the issue of prediction, for example. Science cannot predict earthquakes -- and may never have the ability.

“There doesn’t seem to be a light at the end of the tunnel for prediction,” CGS Supervising Geologist Charles Real said. “What we’ve learned in the last three decades or so is that the earthquake process is highly complex. The number of variables that go into creating an earthquake, and how big that quake gets, is so large and difficult to measure that it has made the development of a good model for how the process works intractable.

“Imagine looking at a freshly plastered wall and trying to predict where the first crack will show up. That’s where we’re at with earthquake prediction right now.”

Real heads the Seismic Hazards Zonation Program for CGS. The program has produced more than 100 regulatory maps showing zones where there’s a relatively higher potential for liquefaction and landslides during large earthquakes.

“My personal feeling is that the ability to predict earthquakes is so far off in the distance that we’re better off expending our resources on learning how to better deal with earthquakes when they happen,” he said. “That’s why our emphasis is on mitigation by defining where earthquakes and associated hazards are most likely to take place, so we can focus our resources toward earthquake-safe development.”

Reichle, who heads CGS’ Seismic Hazards Assessment Program, agrees with Real, saying that science lacks the proper tools to predict earthquakes.

“Before the advent of satellites, weather predictions were rather chancy,” Reichle said. “After there were weather satellites in orbit, meteorologists could see the storms developing in the ocean and do a better job of predicting what would be coming ashore. In earthquake prediction, we haven’t found our equivalent of the weather satellite yet. We don’t have a good prediction tool, and I’m not certain we will ever be able to say with any certainty that there will be an earthquake on this particular section of a fault within the next day or week.”

Instead of prediction, CGS and other scientific organizations have conducted and routinely update probability studies that estimate the likelihood that a rupture will occur on a fault. For example, while the 1987 Loma Prieta earthquake wasn’t predicted, it was centered in an area that was believed to have a relatively high probability of experiencing a large quake.

“We routinely review and revise the probability studies,” said Dr. John Parrish, who heads CGS as the California State Geologist. “We participate on the California Earthquake Prediction Evaluation Council, a group that reviews the predictions of others and advises the Governor and the Office of Emergency Services. But we don’t claim any special insight into when earthquakes will occur – simply the knowledge that they’ve occurred in the past and will occur in the future.”

There are individuals who claim they possess unique knowledge of impending temblors – sort of a “sixth sense.” Supervising Geologist Chris Wills, head of CGS’ Geologic Mapping Program, doesn’t buy that notion.

“Those claims are all based on random chance, as far as I know,” he said. “There’s a magnitude 6 earthquake somewhere in the world about every week. There’s a magnitude 3 in California every day. So it’s pretty easy – and not very helpful – to say something as vague as, `I predict there’s going to be an earthquake soon.’ Earthquakes are frequent enough that sometimes predictions will be right.”

While there are reports of predictions that have accurately stated the time, location and magnitude of an earthquake, frequently such reports aren’t examined in a scientifically rigorous fashion. Wills believe that the human tendency to seek out patterns to make sense of things – as well as selective memory – are behind many claims of inside knowledge of what the Earth is up to.

“Let’s say the bunion on your left foot is sore, and there happens to be an earthquake,” Wills said. “You might remember that and consider your sore bunion a precursor to an earthquake. But you’re probably not going to remember all the times your bunion was sore and there wasn’t an earthquake. It’s just wishful thinking to believe it’s something that simple.”

During a recent total eclipse of the sun, residents of Turkey’s Tokat province camped out in tents, fearing an earthquake. Although the scientific community offered reassurance that there’s no connection between eclipses and quakes, residents remembered that in August 1999, 17,000 people in northwestern Turkey died when an earthquake struck six days after an eclipse.

“Everyone draws connections where they don’t exist,” Wills said. “If you’re a sports fan and your favorite team wins every time you watch the game sitting in a particular chair and loses when you don’t, you may start to think that you have some control over the outcome. You don’t, of course, but everyone wants to find patterns.”

Added Real: “There’s no real physical basis for those type of claims … Frankly, it’s hogwash.”

Speaking of hogs, Real thinks there may be a little something to claims that some animals can sense an impending earthquake.

“There have been some observations that tend to support animal sensitivity,” he said. “In China, there’s a well-known case of successful earthquake prediction based on a variety of evidence, including animal behavior. It was winter (February), and one of the things they observed was snakes that typically hibernate underground coming to the surface only to freeze to death in the days leading up to the earthquake. One wonders what the snakes were sensing.”

The China State Seismological Bureau ordered an evacuation of 1 million people from the city of Haicheng on Feburary 3, 1975. The next day, a magnitude 7.3 earthquake struck; the evacuation probably saved countless lives. However …

“The following year, there was another earthquake that wasn’t predicted (the magnitude 7.8 Tangshan quake),” Reichle said. “Officially, it killed about 250,000 people. Unofficially, it might have killed 600,000. The point is, consistency of the precursors has always been a problem in earthquake prediction research.”

Like his colleague Real, Reichle finds the reports about the behavior of snakes prior to the Haicheng earthquake interesting. Still, he believes from personal experience that animals are just as inconsistent as people when it comes to predicting quakes.

“My cats had no idea that the (magnitude 5.1) Santa Barbara earthquake was coming in 1978,” he said. “They weren’t acting any stranger than normal, and when the quake struck and they bolted, they left wet spots on the carpet. So they were certainly as surprised as I was.”

Wills’ favorite myth comes out of the 1906 earthquake, when it was widely reported that the Earth opened up and swallowed a cow.

“The story went that the Earth opened up, a cow fell into the fissure, and then the Earth closed around it,” Wills said. “A geologist visited the ranch where this happened, and a ranch hand took him to where he could see cow legs sticking up from underground. The real story came out 50 years later, when the ranch hand admitted that he’d found a dead cow that he needed to dispose of. He tipped it into the fissure and covered it with dirt. Fissures open and things can fall in. But the fissures don’t close up.”

Of course, seemingly every fictional portrayal of earthquakes includes a person, car, building or something disappearing into the vengeful soil.

Other favorites include earthquake weather and the notion of California tumbling into the sea.

The notion of earthquake weather can be traced to the Greek philosopher Aristotle in the fourth century B.C. He believed that earthquakes were caused by winds trapped underground in caves. That idea evolved into the belief that still, sultry weather (because of the lack of wind) is associated with quakes.

“The causes of earthquakes happen tens of thousands of feet below the Earth’s surface, while the weather is created in the atmosphere tens of thousands of feet above the Earth’s surface,” Parrish noted. “The tectonic plate boundaries don’t care if it’s sunny or rainy or balmy or freezing.”

Added Reichle: “I grew up in a part of California (Imperial County) that has lots of earthquakes, and I’ve never experienced earthquake weather.”

He doesn’t expect to experience California falling into the Pacific, either, no matter how big the quake.

“The San Andreas fault moves horizontally, not vertically,” he explained. “Los Angeles is moving northwest very slowly. At some point, San Francisco and Los Angeles will be next to each other on either side of the fault. Of course, we’re not going to be around to see it.”

Oh, and about that notion of standing in the doorway during an earthquake?

“For those of us who live in an unreinforced adobe home, it’s the right thing to do,” Parrish said. “But if you’re in a some other type of a building, the doorway is no safer than anywhere else, and perhaps more hazardous. If you’re in an office building and you stand in the doorway, you’re likely to get trampled by people running out. The best bet is to get under a sturdy desk or table and hang on.”

But don’t hang on to misplaced myths.