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Living on the Fault Line

"Those who live in the vicinity are accustomed to earthquakes. But the prospect that scientists now suggest is different from anything within living memory in southern California."

Standing in the wash of the Santa Ana River, you can see mountains all around you. The San Gabriel, the San Bernardino, and the San Jacinto mountains form a long, semicircular are to the north and east pierced by the passes that lead variously to such outposts on the California desert as Barstow, Indio, and Palm Springs. To the south and west are the lower hills that separate the San Bernardino Valley from the booming conurbations of Orange County and from Los Angeles itself, which lies seventy miles due west.

On those days, infrequent during summer, when opaque brown smog has not blown inland to fill the valley and lap over the rim of the mountains, the contours of the ranges are clearly visible from the valley floor. There is no natural obstruction to the view more substantial than the waist-high scrub. The sharp edges and escarpments of the mountains suggest their dramatic origin, as products of the pushes and pulls on the earth's surface that are even now creating mountain ranges in the West. The white gravel in the dry riverbed has been washed own from the mountains during the flash floods that from time to time strike this bone-dry region. The "river" runs with water for only a few days out of every year.

It can seem the bleakest of settings, especially when the Santa Ana winds blow down from the high deserts at temperatures well above 100 degrees. Yet, like many other harsh regions of the Southwest, this has been a scene of phenomenal growth. As people continue to move to southern California, as Los Angeles has filled up, as real estate prices in Orange County have shot to the sky, many people have taken the next step in from the coast and have brought a population explosion to the "Inland Empire." The orange trees that line Interstate Highway 10 are the remnants of groves that were until the past two decades an economic mainstay of the region. They succumbed first to the smog and then to the subdividers. Some 400,000 people lived in the San Bernardino Valley in 1960. More than 700,000 live there now. There are plans for an "instant city" of 200,000 more people, to be built in the hills outside Chino, where the corners of San Bernardino, Orange, and Los Angeles counties touch.

People have moved to this valley seeking cheaper real estate, the good life in the sun, and the opportunities that economic growth creates. They are an hour's drive from the mountains, an hour from the ocean, and far, far away from such northern, urban cares as frost and economic decline. And their search has led them to the area that, according to many scientists, will be the site of the next catastrophic earthquake to strike the continental United States.

Those who live in the vicinity, as I did when I was growing up, are accustomed to earthquakes. Many, pride themselves on surviving them, as those on the Gulf Coast might on surviving a hurricane. But the prospect that scientists now suggest is different from anything within living memory in southern California.

"We have known for years that major earthquakes in California are inevitable," says Clarence Allen, a geophysicist at the California Institute of Technology. "The scientific attitudes have not changed as much as the public perception that this is a real problem." But both scientific and public attitudes have been heavily shaped by two scientific developments of the past decade.

The first, which has been widely publicized since the early 1970s, is the evolution of the theory of plate tectonics. This theory postulates that the earth's crust consists of a number of large "plates," floating on a molten mass within the earth. There are seven of the larger plates—one bearing most of Africa and half of the Atlantic and Indian oceans, another holding virtually all of the European and Asian land mass—and a number of small ones. As the plates have drifted apart from, and into, each other, their motions have changed the world's geography. They opened the basin that became the North Atlantic Ocean, when the North American plate slid away from the Eurasian. They created the Himalayas, which mark the region where India was driven northward and collided with southern Asia. They stimulate volcanic action, including the recent eruptions at Mt. St. Helens. (As the small Juan de Fuca plate is pushed beneath the North American plate off the Washington and Oregon coasts, it melts at the tremendous temperatures and pressures of the earth's depths and then flows upward, in molten form, as lava.) The motion of the plates can also cleave regions from one another, as is now taking place in California.

The most famous of the "faults" that are responsible for California's earthquakes is the San Andreas—which, from the perspective of plate tectonics, is not just any fault but the boundary between two great plates. To the east of the fault lies the North American plate, which contains more than 99 percent of the land area of the nation, along with Canada, Mexico, and roughly half of the Atlantic Ocean. To the west of the fault is the Pacific plate, which runs beneath the ocean to the Mariana trench—where it disappears beneath the Philippine plate. The city of San Francisco is on the North American plate. Santa Cruz and Monterey, immediately to the south, are on the Pacific plate. So are Los Angeles, San Diego, and the other population centers of southern California.

Through the millennia, the two plates have been moving past each other along the San Andreas Fault, the Pacific regions slipping north, the North American south. The Baja California peninsula resembles in length and width an indentation on the western coast of Mexico. That is exactly where it came from, geologists say, before it moved north with the rest of the Pacific plate. The motion of these two plates goes on at rates as high as 5 or 6 centimeters a year—very fast, by geologic standards. Rocks on the Pacific side of the fault near Point Arena match those on the North American side at Taft, 350 miles to the south. The two regions abutted one another until the fault motion started about 25 million years ago. Ten million years from now, Los Angeles and San Francisco should lie in the same latitude.

For California, the significance of the tectonic theory was to explain the basic mechanism of earthquakes, not only on the San Andreas Fault but also on the many others that parallel it and the few that run at right angles to it. Year by year, the plates creep past each other; from time to time, rocks must yield. The largest recent earthquake in California, the 1906 "fire" (as civic boosters chose to call it at the time) in San Francisco, could be seen from the perspective of plate motion as the event through which the northern section of the San Andreas Fault released the strain that had been accumulating over the years.

It took a second and more localized scientific development to add the note of certainty to forecasts that a catastrophic earthquake will strike southern California. The man most often identified with this development is Kerry Sieh, a geologist at Caltech. His contribution has been to estimate the schedule on which the rocks along the fault give way.

As the plates move past each other, the strain that accumulates at great depth can be accommodated in different ways. The plates can release some or all of the strain by "creeping" past each other with steady movement, or through numerous small earthquakes that human beings barely feel. Such creeping takes place along a section of the San Andreas Fault in central California, and it leads to novel effects, such as the fissure at, a frequently photographed winery in Hollister that is gradually being split by the fault. Much of the tension along a fault line can also be relieved through less frequent quakes of "moderate" power, in the range of 5 or 6 on the Richter scale. Many of the subsidiary faults in California behave this way. Finally, the rocks on a fault line can lock solid. When this happens, there is no gradual distortion of roads, fences, or wineries, nor are the earthquakes frequent. The two sides of the fault remain motionless until the shearing force of the plates' movement overwhelms the strength of the rock itself. The result is a "great" earthquake, which releases enormous' accumulated energy all at once and can result in one side, of the fault moving as much as twenty feet past the other, in the space of a few seconds or minutes. The San Francisco quake of 1906 was such a great earthquake, affecting the northern section of the San Andreas Fault. Another portion of the fault, which runs roughly 200 miles between a small town called Parkfield, in central California, and the San Bernardino Valley, and which is sometimes referred to as the southern section of the San Andreas and sometimes as the south central section, has been locked solid for more than a century. In 1857, during its last great earthquake, the sides of the fault moved past each other by as much as thirty feet. The southern most section of the fault, which starts near San Bernardino and runs to the Salton Sea, has had no major ruptures during "historic time"—geologists' term for the 200-plus years of written records for the region, as opposed to the eons of the rocks. Scientists' understanding of this portion of the fault is so incomplete that they are not sure whether it should be considered very likely or very unlikely to suffer a major earthquake in the foreseeable future.

Kerry Sieh's approach was to study the layers of earth at several places along the southern San Andreas Fault to see what they revealed about the timing of previous earthquakes. Through a variety of techniques, such as uncovering layers of peat moss that had been deformed by violent earth movements and then determining their age, he concluded that along the portion of the fault that ends north of San Bernardino, there was a pattern of dormant periods followed by strong earthquakes. Working from an early version of Sieh's findings, the Federal Emergency Management Agency issued the following warning last January as part of a report it prepared for the National Security Council on the consequences of a major earthquake in California:

"Geologists can demonstrate that at least eight major earthquakes have occurred [on the southern San Andreas] in the past 1200 years with an average spacing in time of 140 years, plus or minus 30 years. The last such event occurred in 1857. . . . geologists estimate that the probability for the recurrence of a similar earthquake is currently as large as 2 to 5 per cent per year and greater than 50 per cent in the next 30 years. . . . The aggregate probability for a catastrophic earthquake in the whole of California in the next three decades is well in excess of 50 per cent."

Kerry Sieh has recently reworked his estimates, allowing for greater uncertainty about the magnitude of previous quakes and for the imprecision of the carbon 14 dating process. "The best scientific guess would be that the average interval is somewhere between 125 and 225 years, with both of those being extremes," Sieh said recently. "My own intuitive best guess is that it's about 160 years, plus or minus 30. I'd say that there's a 50 percent chance of a great quake in the next four decades." Considering that the last great earthquake in southern California was 124 years ago, Sieh said at the end of one of his papers, "We are almost certainly not 'overdue' for a repeat of the great 1857 earthquake, but we are clearly well along in the process. We are much too far along, in fact, to neglect serious preparations for the eventuality."

The repeated allusion to "great" earthquakes is important, for it refers to a difference in magnitude so enormous as to become a difference in kind. "Great" quakes are generally understood to be those of magnitude 8 or above on the Richter scale. (Sometimes those of 7.75 magnitude are so classified.)

The last "great" quake in the continental United States was the one in San Francisco in 1906. Since then, Alaska has experienced a great quake, in 1964, and there have been devastating earthquakes in Chile, China, Japan, Italy, and elsewhere. But in California, the strongest earthquakes in the past seventy-five years have been in the 6 and 7 range on the Richter scale—and most of them have been centered in unpopulated areas. The most damaging of the quakes, though not the strongest in Richter terms, were the 1933 earthquake in Long Beach, magnitude 6.3, and the 1971 San Fernando quake, also a magnitude of 6.3. Within a matter of years, there will be no one alive in California with personal memory of the effects of a "great" quake there.

Without the testimony of survivors, it may be hard to imagine the consequences of a "great" earthquake. The difference between 6.3 and 8.3 on the Richter scale does not sound fundamental, but it is. Each increase of 1 on the Richter scale signifies an increase of thirty times the energy and ten times the deflection on seismic measuring devices. If the San Andreas Fault should produce an earthquake of magnitude 8.3, as many geologists expect, it would release, about 900 times as much energy as did the San Fernando earthquake of 1971. (The greatest quake of modern times, which struck Chile in 1960, had a magnitude of 9.5.)

The effects of major earthquakes are more readily comprehensible when expressed in terms of ground shaking, on the "Modified Mercalli Scale." This is a measure of the effects of ground movement as they are felt in specific regions. The scale runs from I to XII. Level I is "Not felt except by a very few under especially favorable circumstances," and II is "Felt only by a few persons at rest, especially on upper floors of buildings." In a "great" quake, large areas may be subjected to the highest intensities of shaking, levels IX through XII:

Level IX: Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb; great in substantial buildings, with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously. Underground pipes broken.
Level X: Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked. Rails bent. Landslides considerable from river banks and steep slopes. Shifted sand and mud. Water splashed (slopped) over banks.
Level XI: Few, if any, (masonry) structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipelines completely out of service. Earth slumps and land slips in soft ground. Rails bent greatly.
Level XII: Damage total. Waves seen on ground surface. Lines of sight and level are destroyed. Objects thrown into the air.

In most versions of the Mercalli scale, levels IX to XII are grouped under the heading "Panic is general."

During the 1971 San Fernando earthquake, in which highway overpasses collapsed and forty-five people were killed when a Veterans Administration hospital fell down, there were shaking intensities of IX and perhaps even higher in some areas near the epicenter. The California Division of Mines and Geology has produced maps that display the predicted shaking intensities for a great quake on the southern San Andreas Fault. They show bands of IX intensity stretching for more than 100 miles, with levels of X to XII expected in sizable zones.

As the descriptions on the Mercalli scale may suggest, the main threat to human life during an earthquake comes not from the earth's movement itself but from things that fall. When severe quakes have occurred in out-of-the-way places, such as the 1872 earthquake in Owens Valley, they have rearranged the landscape but have taken comparatively few lives. That earthquake, centered in the stark region east of the Sierra Nevada Mountains, was the strongest in California's history—its force was so great that within seconds it added ten to fifteen feet to the height of an escarpment and moved the sides of the fault twenty feet past each other—but only sixty people were killed. Unless people are trapped in the path of a landslide, hit by falling trees, or drowned by the large ocean waves, called tsunamis, that earthquakes sometimes produce, they face little danger if they find themselves out in the open when an earthquake strikes.

The danger comes instead from buildings, especially those made of brick and other masonry, that are shaken to pieces during strong earthquakes and, in falling, cause most of the deaths. Some of the unreinforced brownstones of Manhattan, Federal townhouses in the Georgetown section of Washington, D.C., and mansions along Commonwealth Avenue in Boston, all so solidly built, could be converted to rubble in an earthquake, for their style of construction is generally the first to fail during strong quakes. Wood-frame houses, by contrast, are the most stable structures, since they are able to sway and absorb the earth's motion. Only under the most severe shaking intensities do one-story frame houses collapse.

The ability of different buildings to withstand shock is also greatly influenced by the ground on which they stand. The best place to be during a strong earthquake is on solid rock; the worst is on soft ground, mud, landfill, or areas with a high water table. Rock diminishes the intensity of the shaking; soft earth magnifies it. This principle is not limited to California. If a strong earthquake were to hit Boston (which is a less remote possibility than it may seem, since Boston has historically been one of the more seismically active areas in the East), the houses of the Back Bay would be most severely shaken, because they are built on landfill. In 1906, the regions of San Francisco built on reclaimed land near the bay were far more heavily damaged than buildings on top of the city's rocky hills. The ultimate danger in such areas is liquefaction, caused by violent shaking that drives groundwater upward through the soil and thereby transforms it to quicksand. Heavy buildings, especially multistory structures that are not anchored in bedrock, can tip over or sink into soil after it liquefies.

Through most of its southern section, the San Andreas Fault traverses dry plains and rocky canyons, where there are few buildings to destroy. But after it crosses through the San Bernardino Mountains at the Cajon Pass, it enters the inland valley that is now supporting such rapid growth, and it comes at its nearest point within about thirty-five miles of Los Angeles. It is the combination of the increasing probability of a quake, its expected magnitude, and its nearness to such a vast and wealthy human settlement that has created an atmosphere of concern about an earthquake on the southern San Andreas. Two other possible earthquakes are on the list of concerns: a major quake on the northern San Andreas, which is thought to be less likely, since only seventy-five years have passed since the San Francisco earthquake, but which would affect an even more densely populated area and therefore might be more devastating; and a moderate earthquake on the Newport-Inglewood Fault, which runs directly through Los Angeles and was responsible for the Long Beach earthquake of 1933. Statistically, the latter is thought to be a longer shot than either of the others, but because it would affect Los Angeles directly, it might be the most damaging of all.

Shortly after Jimmy Carter took a tour of the landscape of devastation around Mt. St. Helens, he grew concerned about the effects of a catastrophe in California and ordered a federal task force to prepare a report. Based on assumptions about how many people would be killed in different kinds of structures (for instance, 2 to 4 deaths per 10,000 population in wood—frame houses, 5,000 deaths per 10,000 in ordinary masonry buildings), the task force came up with the following estimates of deaths and of injuries serious enough to require hospitalization. Some of the situations it considered were these:

Location Southern San Andreas Newport-Inglewood Northern San Andreas
Richter Magnitude 8.3 7.5 8.3
    Dead / Injured Dead / Injured Dead / Injured
  2:30 A.M. 3,000 / 12,000 4,000 / 18,000 3,000 / 12,000
Time 2:00 P.M. 12,000 / 50,000 21,000 / 83,000 10,000 / 37,000
  4:30 P.M. 14,000 / 55,000 23,000 / 91,000 11,000 / 44,000

In addition, there is, of course, the property damage. A consultant named Karl Steinbrugge, who was responsible for many of the most widely circulated damage estimates, predicted that the property damage could amount to some $17 billion for the southern San Andreas, $38 billion for the northern, and $69 billion for the Newport—Inglewood. Because of the enormous uncertainties about both the quakes and the resistance of structures, Steinbrugge stressed that any of the estimates might be off by a factor of two or three—either high or low.

In 1973, the National Oceanic and Atmospheric Administration, known as NOAA, prepared two thick volumes to enumerate the likely effects of a major earthquake in Los Angeles and of one in San Francisco. The books contain page after page of maps, each one plotting the two major faults in northern and southern California and showing their location in relation to major facilities: hospitals, blood banks, reservoirs, railroads, airports, highways, military bases, aqueducts, natural-gas lines, electric generating stations and transmission lines, oil pipelines, and other facilities. The southern California report says, for example, that a major quake on the San Andreas could kill between 400 and 800 people who are already in hospitals and put 50 percent or more of hospital beds out of commission, at precisely the time that the demand for emergency service would be most intense. It also says that "in the event of an 8.3 magnitude shock on the San Andreas Fault, the failures of Fairmont and Bouquet Canyon dams should be assumed," and that such failures could kill more than 7,500 people and render 111,000 homeless; that all of the aqueducts that serve Los Angeles and San Bernardino cross the San Andreas Fault at least once and one of them crosses it four times, and that the region may be without its major water supplies for between two weeks and three months after a quake; that transportation, communications, finance, and all other essential services would be interrupted.

After reviewing these and other predictions, the Federal Emergency Management Agency concluded in its report earlier this year that "the Nation is essentially unprepared for the catastrophic earthquake (with a probability greater than 50 percent) that must be expected in California in the next three decades. Because of the large concentration of population and industry, the impacts of such an earthquake would surpass those of any natural disaster thus far experienced by the Nation. Indeed, the United States has not suffered any disaster of this magnitude on its own territory since the Civil War."

"What must be stressed is that this prospect presents us with an unprecedented problem in the history of the United States," Carl Ledbetter, a young mathematician who was briefly the director of the Southern California Earthquake Preparedness Project, said earlier this year in testimony before a congressional committee. "There has been no other time when the lives of as many as 69,000 people have been threatened at once; there has been no other time when losses on the order of magnitude of $135 billion have been a real consideration; there has been no other time when the productive capacity of a region which generates one dollar in twelve of the country's Gross National Product has been under such a real and unavoidable threat.

"We do not know how to think about threats of this magnitude; they are unreasonable by all our past standards."

Some scientists seem to feel that they do know how to think about such threats. They are concentrating on finding ways to predict when and where earthquakes will occur. From experience in the U.S. and more advanced work in the Soviet Union, Japan, and China, geologists have focused on several signs that usually appear from several months to several hours before large earthquakes occur.

One such sign is a pattern of small "foreshocks" that leads to a major shock. ("The problem is distinguishing between those and other patterns that don't turn out to be foreshocks, because no large earthquake follows them," says Karen McNally, another of Caltech's geophysicists.) The Chinese have associated the period before large earthquakes with changes in the nature and behavior of groundwater. The water level in wells sometimes changes just before a quake, and the water may contain different concentrations of radon gas. Both of these changes are apparently signs of rearrangements in the underground rock layers, which affect the courses through which the water must pass. Other scientists have constructed grids of geodetic markers on the earth's surface near a fault, on which they take repeated measurements to determine how much the earth's accumulating strain has distorted the grid.

There are even attempts under way to make scientific sense of the familiar folk-wisdom reports that animals can tell when an earthquake is coming on. In central California, near the San Andreas Fault, one researcher has built a number of burrows for field mice and monitored them to record the animals' activities. He will attempt to establish the normal patterns and the variations from them for seasons and for feeding cycles—and then he will wait for the next big earthquake.

"We need more time—and we need more earthquakes," says Karen McNally. Few phrases are more frequently heard from the geologists and seismologists than "We'll learn a lot from the next big one." Such knowledge may be costly. Clarence Allen, in discussing events of the past year or two, says, "There's been a change in the seismic pattern [in southern California] that makes us more worried than we'd normally be. We know we're in an area and an era where a great earthquake would be no scientific surprise. We see a pattern of low activity for fifteen years or so—and now this change to higher activity, which makes us nervous." There are similar implications from the Palmdale Bulge, an area along the San Andreas Fault north of Los Angeles where the ground has apparently risen about a foot. "On the assumption that the bulge exists, as I would argue it does, it may be significant," Allen says. "Its shape is roughly coincident with the fault, and the very rapid rate of its rise—by geological standards—makes us think it might be trying to tell us something." But just what the bulge—or the changed seismic pattern, or the groundwater, or the animals—may be trying to say will be much clearer after the next big earthquake has confirmed or disproved the hypotheses.

In the meantime, of course, scientists are offering forecasts whose details of time and place may be imprecise but whose general point is hard to miss. But because the day of reckoning is so uncertain, and because the catastrophe is so strongly associated with divine judgment, against which the efforts of mortals are no defense, it has been hard for California and its public officials to decide what to do.

The things that could conceivably be done fall into two categories—mitigation and preparedness. Mitigation means taking steps before an earthquake to minimize the damage; preparedness means being ready to cope with the problems created by the earthquake.

Since earthquakes do most of their damage to buildings, the most obvious mitigating procedure is to strengthen buildings that might otherwise be destroyed. This California has tried to do, by passing new laws and tightening its building codes after each serious earthquake. When the 1933 Long Beach earthquake crushed masonry buildings throughout southern California, including a large number of schools, people realized that if the earthquake had occurred a few hours earlier, when school was in session, thousands of children might have been killed. The result was the Field Act, which set more stringent standards for school construction and, despite some delays in application, has made schools the safest public buildings in the state. During the 1971 San Fernando earthquake, the Van Norman Dam was so severely damaged that, according to most experts, it came within a few seconds' shaking of failing altogether. If it had done so, the death toll from that earthquake might have increased by a factor of 100. Soon afterward, the state undertook a dam inspection program that has—theoretically—made its dams much safer than before. The improvement must so far be considered only theoretical, because neither the dams nor the skyscrapers that have sprung up in Los Angeles since the thirteen-story limit on construction was removed in 1956 have yet been subjected to the test of a major quake. Engineers have often found themselves chagrined by the results of previous quakes. In 1979, a 6.6 magnitude quake struck the Imperial Valley, an earthquake-prone region east of San Diego. The most serious single casualty was the Imperial County Services Building, a new six-story structure that had been advertised as incorporating the latest standards in earthquake-resistance but which was so severely damaged that it had to be demolished.

The major structural peril is the large stock of old (pre-1934), unreinforced masonry buildings. There are about 8,000 of them in the city of Los Angeles alone, and their inevitable destruction is expected to be responsible for 80 percent of the deaths and 75 percent of the injuries in a great earthquake. The buildings are located mainly in the crowded downtown areas of Los Angeles and in the less fashionable sections of San Bernardino and other cities. The population that lives and works in them is largely poor and non-white, which is why earthquakes—though they threaten Porsche and pickup alike when freeway bridges collapse—will probably end up killing a disproportionate number of poor people. The economic forces that have kept the old buildings from being reinforced or renovated during the previous fifty years also make the owners of the buildings unlikely to invest voluntarily in such reconstruction. Early this year, the Los Angeles City Council passed an ordinance requiring that all the old buildings be either greatly strengthened or razed.

While earthquake experts generally praise this step, they point out two catches: the deadline for renovation is a dozen years away and could be stretched out even further through legal maneuvering; and no one has figured out who should pay the bill. One school of thought contends that anyone who bought one of these buildings knew there was a hazard and has no right to complain because the gamble didn't work out. Others argue that strengthening the old buildings and reducing the potential disaster serves the public's interest and therefore deserves public financial support, through either tax incentives or low-cost loans. Still another group claims that trying to repair these structures before a quake will always be too costly to make sense. "You can't talk about a massive program of retrofitting old buildings," says Richard Andrews, the acting director of the Southern California Earthquakes Preparedness Project. "If you're talking about a building still under construction, making it seismically resistant might add 5 to 7 percent to the cost. For those that are already built, it can add 100 percent." Instead of worrying about avoiding property damage, some earthquake authorities conclude, it makes better sense to assume that the scientists will provide some warning, and then to get people away from the buildings and out of harm's way when an earthquake is due.

In a more fundamental sense, mitigation includes not only the buildings but also the places where they are built. From this perspective, the population boom in northern San Bernardino County can be seen as a move in the wrong direction. The northern outskirts of San Bernardino and the surrounding small communities—Del Rosa, Highland, Patton, Devore—are dotted with tract homes and new condominium developments. This very region is the southern limit of the 200-mile ground rupture that can be expected if the next great earthquake follows the pattern of the one in 1857. The geological map shows that the San Andreas and several associated faults pass directly through the new developments.

Since 1972, construction near fault zones has been controlled by California's Aiquist-Priolo Act, which declares the areas near active faults to be "special study zones" and forbids construction intended for human occupancy within fifty feet of the trace (surface line) of an active fault. I visited one of the largest condominium developments north of San Bernardino, a place with several hundred units—adults-only apartments plus an adjoining mobile-home park. "You may have noticed some wide yards, some extra swaths of grass," Robert Rigney, the county administrative officer for San Bernardino County, later remarked. "Those represent the geologists' best guess about where the fault line runs." When I asked the saleswoman at the development whether there were any earthquake problems in the area, she said, "This is southern California, honey. This is earthquake country. You ever look at a fault map? There's no place you can go that's very far away from them, so my advice is just to forget about it."

Indeed, Robert Rigney says that nearness to the fault, as in the case of this development, could be a source of false alarm. "The fifty-foot limit was designed to protect structures from damage caused by ground ruptures," he says. "Once you've passed that point, proximity doesn't mean much. As for the shaking—well, the whole valley will have that." As Clarence Allen puts it, "In a truly great quake, once you're a few feet away from the rupture it doesn't make much difference whether you're there or five miles away."

Robert Rigney also raises a larger question. Should people be prohibited from doing something—like buying new houses near the fault line—that may well cause them harm? "The zoning laws are designed to protect against injuries and deaths, especially in public buildings. They are not intended to protect property per se. If people choose to live here, that's their choice."

In a sense, he's right. The sociologists whose reports make up a larger and larger fraction of official publications about earthquakes have consistently pointed out that among all the possible responses to warnings of a quake, moving away from southern California is the public's last choice. "The Southern California public's lack of readiness is quite rational," a report from the Policy Research Center at the University of Redlands said early this year. "The threat is too uncertain in its impact and timing to command a high priority with people, especially since they face more pressing life demands which justify higher costs and yield higher immediate benefits. Just as people accept the risk of driving a car in order to gain the freedom it allows, many residents may also consider the earthquake threat an 'acceptable risk' in light of the benefits of living in Southern California."

The only thing wrong with the idea that people have knowingly accepted a risk is that many of them don't have the slightest idea what the risk really is. The most widespread source of misinformation is the notion that, since nearly everyone in California has lived through some earthquakes, they have a rough sense of what a big earthquake would be like. When I moved away from California in the late 1960s, I mocked the fears of my eastern friends about the effects of a quake. I'd been there; I knew what they could do. My confidence was eroded recently, when I discovered that during the period I lived there the strongest earthquake to strike southern California was 4.5 on the Richter scale—about a millionth as strong as the big one that is predicted.

Giving people more of the basic information about faults, earthquakes, and hazards is a principal mission of one of the most hopeful new entries in the earthquake field, the Southern California Earthquake Preparedness Project. The project was launched as a cooperative effort of the federal government and the state. Its major purpose was to bring government officials, industrialists, and scientists together so that they could start figuring out who would do what to repair the damage done by the big earthquake. Who would fly in enough cash to keep the local economy running during the weeks it might take to reconstruct bank records lost when the computers go down? ("They tell us it will take ten days to get restarted for every one day the system's out," says Richard Andrews, of the project.) Who will run the morgues? Who will handle the insurance companies, if there is a prediction of a quake nine months from now and they start refusing to renew earthquake coverage?

The project has been hampered in its early stages by a messy disagreement between Robert Olson, who as director of California's Seismic Safety Commission has administrative jurisdiction over the project, and Carl Ledbetter, the mathematician and academic administrator who, at the age of thirty-one, was hired as the project's first director in January of this year. In July, Ledbetter submitted his resignation after Olson had asked him to do so. Olson claims that the disagreement was purely one of personal tastes and administrative styles. Although Ledbetter himself does not say so, others feel that he had made some officials nervous, even envious, because of his very success in getting the press and the public to begin thinking of earthquakes as a serious threat.

The disagreement about the southern California project may have been largely a clash of personalities, but it rises above that to the extent that it illustrates the internal friction that has characterized many efforts to "do something" about earthquakes. Most of the public bodies that have wrestled with the earthquake problem seem to have proven more successful so far in accommodating their own professional and bureaucratic habits than in doing things that would make a significant difference if a great earthquake should strike, say, next month. For politicians, those habits include making gestures of concern. Thus, Governor Edmund Brown, Jr., has appointed a special task force to look into earthquakes; its findings are not notably different from the many reports that other task forces have written and filed over the years. For sociologists, earthquakes provide a reason for polls differentiating between "elite" and "mass" views on, for example, the credibility of earthquake warnings delivered through different news media. The "public policy" consultants have seen in earthquakes an opportunity for constructing elaborate flow charts and "decision trees" of phenomenal complexity, much as their professional brethren did fifteen years ago when laying plans for Model Cities and the Job Corps. Meanwhile, new houses spring up near the fault zone and old houses stand waiting to collapse.

There also seems to be a genial agreement among many of the participants that ignorance is bliss. If there is a constant in the political history of earthquakes in California, it is that responsible officials are often eager to promote the idea that it can't happen here. Arnold Meltsner, of the University of California, has pointed out that "the geological map of California published by the California State Mining Bureau in 1916 did not contain any indication of faults, not even the famous San Andreas"—and this ten years after the San Francisco earthquake. Representatives of Palmdale have done their best to have their bulge referred to instead as the "Southern California uplift." When officials of a county in southern California discuss what their role after an earthquake should be, they tend to emphasize what they will be doing to help repair the devastation elsewhere, not what help they themselves will need.

Any non-Californian who is tempted to mock the desire to ignore earthquakes is invited to consider his own situation. While the government's seismic-risk maps show that most of California is in Zone 3, where "major destructive earthquakes may occur," that zone is not confined to California. It also includes parts of Utah and Idaho; the area along the Mississippi where Arkansas, Missouri, Tennessee, and Kentucky meet; the Charleston region in South Carolina; greater Boston; a strip along the Great Lakes; and the St. Lawrence Valley in upstate New York and northern Maine. For several months in the winter of 1811-1812, a powerful sequence of earthquakes occurred in New Madrid, Missouri. In 1886 there was another powerful earthquake in Charleston, South Carolina.

I asked Clarence Allen what caused those earthquakes. He said, "No one knows."

On a smoggy summer day when the temperature was 99 degrees, Carl Ledbetter rode with me through the foothills north of San Bernardino where the San Andreas Fault runs. "If I remember the maps correctly, the fault goes right past this intersection," he said as we stopped at a crossroads. On one corner of the intersection was a mobile-home park.

"Mobile homes are tremendously vulnerable during earthquakes," Ledbetter said. "They suffer about six times as much damage as regular homes. All of these will be thrown off their supports. They'll all be gone." We drove up a steep hillside, where several dozen new single-family homes were ready for occupancy. "You see the grading on the terraces here? That will never hold. There will be landslides all down this hill."

We drove back down the hill, to the floor of the Santa Ana wash. Farther, to the east, where the San Andreas Fault began to divide into two roughly parallel zones, there was a narrow, sharply defined ridge, of the sort that is sometimes created by fault action. Several modern, obviously expensive houses sat on top of the ridge. "I've got to bring my camera up here and take 'before' pictures of all these places," Ledbetter remarked. "Then I'll come back for the 'after.'"

"We could do something about it," he said, as we drove through the wash to Redlands. "Little things can make a big difference, like strapping down the water heater to ensure you'll have something to drink, or knowing how to turn off the gas lines and prevent a fire. Also big things, like thinking about land-use policies, and being prepared for a big earthquake's impact on the nation's economy and its military security. It's not impossible to protect ourselves. But we'd have to start doing it now."