All Shook Up

Kenneth Reich is a Times columnist and occasional writer on earthquakes

In California geology, time has been both a blessing and a problem. A blessing, because devastating earthquakes or volcanic eruptions do not occur all that often. (In this century, there have been seven quakes qualifying as seriously destructive in the state's urban areas--four in the Los Angeles area--and just one volcano that became active, Lassen Peak, in 1914-21.) But time is also a problem because memories of such events seem to fade quickly as a constructive influence on public policy. Quite simply, much of California's population is in denial of the earthquake danger, and there is little pressure on the state's political leadership to do much to assuage it.

Earthquakes and volcanic eruptions simply do not occur with enough frequency for us as a society to be encouraged to take the additional precautions to avoid heavy damage and loss of life in the future.

It is easier to neglect taking action, and "The Earth in Turmoil" and "Magnitude 8," while dramatizing the occurrence of such disasters, also stress our inability to predict them. Both books show that seismology is a highly frustrating science. Whereas a chemical reaction can be closely observed in a controlled setting in plain view of a scientist, an earthquake occurs miles beneath the Earth's surface, and its causes and processes remain unobserved and extremely mysterious. There have been instrumental advances, and better understanding exists now than in the last century, but earthquake science is still, in many respects, akin to reading tea leaves. Of these two books, Philip Fradkin's is particularly skeptical of the present state of the science.

While researchers can describe what has occurred in past earthquakes and volcanic eruptions, they still have limited knowledge about what exactly triggers them and when they will occur or how big they will be. Needless to say, such knowledge would facilitate the organization of timely preventive measures by state and local government. Some highly useful and relatively less costly ones have already been undertaken, beginning after the 1933 Long Beach earthquake. California has developed building codes that restrict vulnerable brick masonry buildings and some unreinforced concrete structures. And the state has been retrofitting highway bridges.

But very little has been done to ban construction in the riskiest zones, aside from the relatively weak Alquist-Priolo law that prohibits building directly on active faults. And the state has scarcely dealt with parts of the building code such as those sections concerning tilt-ups, that were proven deficient by the 1994 Northridge earthquake. And it has not yet discovered how to protect high-rise buildings whose steel frames showed a distressing tendency to crack in that earthquake.

There is, however, little sense of urgency, because no one knows how much time we have before the next catastrophe. It is easy to dither.

In "The Earth in Turmoil," Kerry Sieh, a geology professor at Caltech, and Simon LeVay, a science writer and neuroscientist who has taught at Harvard Medical School, have written a scholarly book that outlines the latest tectonic theories and analyzes in detail key events, such as the Mount St. Helen's eruption of 1980 and the earthquakes along the San Andreas fault.

Sieh and LeVay demonstrate the impact of scientific uncertainty on public safety efforts in a key chapter on the volcanism at Mammoth Lakes in the Eastern Sierra, 275 miles north of Los Angeles. The authors tellingly quote Nancy O'Kelly, president of the local Rotary Club, as expressing the view that public concern over potential geologic disasters in that region is low because the geologists monitoring Mammoth haven't done a good job of communicating those dangers clearly.

"Their language is much different in that they talk in long periods of time," she tells the authors. " 'Imminent' does not mean imminent to them." And O'Kelly laments the confusion that exists in the scientific community as to just how devastating an eruption, when it does occur, will be. (After all, one eruption 760,000 years ago in the Mammoth area would, if it ever recurred, destroy much life throughout the western United States. Fortunately, although there have been many eruptions since, none of them have come close to its size or impact.)

The authors properly defend the scientists, who are confronted by many questions that have no certain answer. They find the chief Mammoth monitor for the U.S. Geological Survey, David Hill, to be "far more guarded" in his views about the potential severity of an eruption than even the townspeople perceive. "He would like to be able to make a quantitative estimate of the probability of an eruption, as is increasingly being done in the field of earthquake forecasting," they observe. "As a start . . . he points out that over the past few millennia, magmatic eruptions have taken place (near Mammoth Lakes) at intervals of about 200 to 700 years. The 'background probability' of an eruption in any given year is therefore one in a few hundred. This background probability has to be raised, however, to take into account the current unrest in the caldera. How much it should be raised is the fundamental problem, which presently defies solution."

But with a 500-year spread of uncertainty between even small Mammoth eruptions, no wonder residents are impatient with the scientists, not to mention alarmist news and television reports that sporadic earthquakes may portend immediate catastrophic volcanic activity.

In fact, as Fradkin points out in "Magnitude 8," quantitative estimates even of the probability of earthquakes have been unreliable. Fradkin devotes a critical chapter to the most specific (and, unfortunately, wrong) prediction California scientists have yet made of an impending earthquake: at Parkfield, a hamlet astride the San Andreas fault in central California.

In 1985, scientists stated there was a 95% probability that a shock of about 6 magnitude would occur near Parkfield by 1993. But no such quake occurred. Fradkin, an environmentalist, journalist and the author of six books on the American West, observes that there were subsequently 100 alerts, but "by the early 1990s, it was clear to the seismological community that something had not worked." The prediction has not been realized yet.

Fradkin makes a great deal of the failure to predict an earthquake in an 8-year period. But in their book's conclusion, Sieh and LeVay emphasize that the pertinent times in California seismology are much longer than that. They note that Californians like to speak about movement on the San Andreas fault that eventually will see Los Angeles sliding past San Francisco. But that will take an unimaginably long time. In 100,000 years at historic slip rates, they point out, "the San Andreas fault will have slipped by a mere two miles." So, they tell us, we need not worry personally about Los Angeles moving north of San Francisco.

Fradkin, who has written a more impressionistic and pessimistic book than Sieh and LeVay, observes that California has, in the 20th century, been lucky with timing and placement of quakes. Frequently, the biggest ones have occurred in the early morning, when children are not in schools or families dispersed, or workers in offices where contents fly around.

He also notes the many instances in which reports written about the effects of serious quakes are missing or were never adequately prepared. "Whether suppressed, nonexistent or simply disregarded at the time, [this oversight] made little difference," he declares. "No report on an earthquake, either then or now, has affected public policy. Reports on this subject--even very good ones--are not popular."

Fradkin concludes with these foreboding words: "I fervently hoped that I would miss the inevitable moment when California finally ran out of luck." Those Californians not in denial may find it worthwhile to understand, according to "The Earth in Turmoil" and "Magnitude 8," that we live on the edge, both metaphorically and literally.

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