Science / Medicine : A Shaker in the World of Earthquake Studies : Seismology: Lucile Jones is one of the first--and most widely publicized--experts to speak up when a temblor hits. Her goal is to determine the probability of the next one.

An earthquake has struck in Southern California. By the score, newspaper and television reporters rush to the Caltech Seismological Laboratory in Pasadena, which has become in recent years the center for information on such occasions.

Amid the numerous seismographic machines, in the most crowded conditions, the news people struggle for position, while an array of earthquake experts tell what they know and try to put the quake into context. A representative of the state Office of Emergency Services is usually on hand to give the official damage reports.

Almost always at the center of this confusing scene is Lucile M. Jones, a seismologist from the U.S. Geological Survey’s Southern California field office across the street from Caltech. Jones, 35, also is a visiting research associate at the Caltech laboratory, where her husband, Egill Hauksson, is a seismologist.

Since she arrived in Pasadena in 1983, Jones has gradually emerged as the most outspoken and often the most publicized seismologist in this area. This fall, when the NBC network plans to air its four-hour miniseries, “The Great Los Angeles Earthquake,” the lead actress, playing a government seismologist, will be modeled to a considerable extent after her.

Frequently, Jones is first with a detailed analysis of what has happened in an earthquake, and sometimes her views have a twist that is different from others. A quick study, she not only frequently makes up her mind within the hour, but unlike some of her more reticent colleagues, she is ready to express a developing consensus among seismologists before anyone else will talk about it.

“Communications with the press, explaining matters and, often, being able to reassure the public is one of the most important things we do,” Jones said.

Last fall, for example, Jones created a stir when she declared within a day that the devastating 7.1 magnitude Loma Prieta earthquake that shook the Bay Area was more a vertical-thrust quake than the conventional strike-slip, or horizontal, quake usually associated with the San Andreas Fault.

In fact, Jones suggested, the temblor might not have been precisely on the main San Andreas at all, although she joined others in concluding it was within the San Andreas system.

Although seismologists stationed at the Geological Survey’s much larger regional office at Menlo Park later acknowledged the accuracy of much of what Jones had said, they also left little doubt that they wished she had not made her comments when she did, or where she did, hundreds of miles away in Southern California.

As Jones later acknowledged, her speaking out had violated an informal agreement under which Geological Survey seismologists in Northern California do not talk publicly, at least first, about Southern California earthquakes, while the ones in Southern California don’t talk about Northern California ones.

It may have been irrepressibility, rather than any bad intent, which led Jones into the contretemps, and maybe all the clamoring of Southern California reporters for information had something to do with it too.

The important thing is that Jones is a highly knowledgeable, well-educated and experienced seismologist and geophysicist, and she is going to be noticed, not least because she has become deeply involved in the intriguing science of assigning probability to the occurrence of larger earthquakes after small ones strike.

From 1979, when she went to China as an MIT graduate student to study foreshocks of the 1975 Haicheng earthquake--the first American scientist to work there after normalization of relations--Jones says she has been fascinated by the prospect of giving some warning of at least some big quakes.

“About half of all big earthquakes are preceded by a foreshock within three days,” she noted. “And about 6% of all small quakes are followed by a bigger one in three days. One quarter of those larger quakes occur within the first hour of the foreshock.” These are conclusions Jones and her colleagues have reached after years of study and statistical analysis.

Furthermore, Jones noted, in some parts of California’s biggest fault systems, the probability of, say, a 5 magnitude earthquake being followed by a bigger one is greater than 6%. It may be 24% in some parts of Central California, according to analyses that have recently won wide acceptance in the California geological community.

Jones, nonetheless, created a stir in May when she was quoted as saying that a computer program being developed could declare the probability of big earthquakes after small ones had occurred. She says now that she was misunderstood and it is not so simple as putting it in a computer. Computers are tools that are used in the analysis, she says.

Still, study of major fault systems in California has proceeded to the point where it is becoming possible to issue warnings of a higher-than-normal probability of a big earthquake in various areas, Jones says, and she thinks that if that probability is only 5% in a three-day period, it is still worth doing.

Authorities can use such information to take certain precautions, such as canceling vacations of disaster personnel or moving fire trucks and other vital survival equipment out of buildings exposed to damage. Even ordinary citizens might, for example, fill bathtubs with water to be used if supplies are later cut off.

Jones, currently on maternity leave, said in a recent interview that she feels earthquake prediction has been oversold, if by that it is meant that scientists will someday be able to warn people that an earthquake is bound to occur at a particular site at a particular time. But probability analysis is a different story, “and as we learn (more), the probabilities we are able to assign will increase,” she said.

Born in 1955 in Santa Monica and descended from American missionaries and academicians in China, Jones gained an interest in that region that ultimately was to become a turning point in her scientific career.

In high school, she spent a year as an exchange student in Taiwan, and then, while a physics and Chinese language student at Brown University, she was able to spend another year in Taiwan in a Stanford-administered study program.

“You either become obsessed with the study of Chinese or you give up,” she said.

It was not until she returned to Brown, in her senior year, that Jones took her first geology course.

“I was hooked within a week,” she recalls. “Part of it was that the jobs in physics basically are building bombs. In geology, you could go play in the mountains and get somebody to pay for it.”

She was accepted into a graduate geology program at MIT, where she received a doctorate in geophysics in 1981. But in the meantime, she had participated in field studies in tectonics in Afghanistan and done the foreshock analysis work in China.

Jones recalls Afghanistan as a trial. “Women are bought and sold in Afghanistan,” she said. “My adviser was offered two camels for me, double the going rate.”

She went to China in early 1979, becoming a researcher at the State Seismology Bureau in Beijing, the Chinese equivalent of the U.S. Geological Survey.

In the study of foreshocks, Jones says that she and other scientists have tried for years to find discriminating characteristics between foreshocks of major quakes and other small quakes that are not followed by larger ones. But so far, no such sure discriminating characteristics have been discovered.

“Are foreshocks even theoretically different?” she asks. “Or are foreshocks just earthquakes whose aftershocks get too big? Are they the straw that breaks the camel’s back and brings on a large quake--a trigger--or are they main shocks that are trying to get started and, for some reason, temporarily get hung up?”

All that is known for sure, she says, is that some percentage of the time small shocks are followed by larger ones, but whether this can ever be expressed in a model as a set of firm probabilities is not so certain.

After receiving her Ph.D., Jones was a post-doctoral fellow at the Lamont-Doherty Geological Observatory of Columbia University from 1981 to 1983 and then joined the Geological Survey as a National Research Council Fellow in 1983 in Pasadena. That fellowship lasted for two years and then, in 1985, she became a geophysicist assigned to the survey’s Pasadena office.

Despite her earthquake studies going back a dozen years, Jones had, in her words, until recently “done an excellent job of missing earthquakes.” She didn’t feel the 1987 Whittier quake, because she was in an automobile at the time.

But she has felt some of the more recent Southern California temblors, and thinks of them as a spur to her work. “It’s made it a lot more fun and a lot more immediate,” she said.