by John Dvorak
Elsewhere, the shaking caused 12 overpass bridges to crash onto freeway lanes. Fortunately, the earthquake struck in the early morning hours and few vehicles were on the freeway, though Clarence Dean of the Los Angeles Police Department died when he was unable to stop his motorcycle before it ran off a partially collapsed bridge. The greatest concern—even outdoing the damage to the hospitals—was the failure of the Lower Van Norman Dam.
Built in 1916 to hold water coming into the Los Angeles area via the Owens Valley aqueduct, the Lower Van Norman Dam was an earth-fill dam consisting of a clay core covered with a thick layer of sand. The shaking had caused the upstream part of the sand layer and part of the clay core to slide into the water reservoir, leaving only four feet of freeboard between the water level and the top of the now-damaged dam. Eighty thousand people who lived downstream were evacuated immediately. The dam was repaired and the people returned.
The 1971 San Fernando earthquake, which at magnitude 6.5 is regarded as a moderate event, was the first damaging earthquake in the Los Angeles area since 1933. It showed how inadequately prepared California was for a truly large earthquake. It also set off a renewed interest in reducing hazards related to earthquakes, and brought forth the harsh reality that while the annual average of deaths by earthquakes might statistically only be ten per year, it would only take one catastrophic incident to make that number rise exponentially.
On November 21, 1972, the Hospital Safety Act was signed, which required the same strict building standards be applied to hospitals that were already—as a result of the 1933 Long Beach earthquake—applied to public schools. A month later, another legislative act was signed that prohibited the construction of new houses within 500 feet of an active fault—to lessen the possibility that an earthquake rupture might form in someone’s backyard or through their bedroom. And in December 1974 the California Seismic Safety Commission was established to advise the governor on future programs needed to reduce earthquake risk. But there was nothing about prediction.
In 1971, the failed forecast by psychic Elizabeth Steen was still fresh in people’s minds. And for years after 1971, Reuben Greenspan kept telling anyone who would listen that he had predicted the earthquake two days before it occurred. By the time the Seismic Safety Commission was organized, The Jupiter Effect was selling well, its contents regarded by some as a justifiable end to a hedonist society.
And yet, though Frank Press tried to find support, the 1971 San Fernando earthquake was still not enough to direct interest toward earthquake prediction. Instead, as Press now realized, such a redirection would require a truly colossal event and the startling claim that some credible person—or persons—had predicted it. That claim came in February 1975 when rumors circulated that Chinese scientists had successfully predicted a destructive earthquake 24 hours before it occurred, and as a result forced the evacuation of a large city, thereby saving hundreds of thousands of lives.
Haicheng is located about 300 miles northeast of Beijing in Liaoning Province. In 1975 it had a population of about 1,000,000. It is a mining center, touting itself today as “the talc and magnesium capital of the world.” To seismologists, it is the site of the only successful prediction of a major earthquake—with qualifications.
Beginning in September 1974, many small local earthquakes were recorded by Shipengyu Earthquake Observatory, located 15 miles from Haicheng. On December 22, the first widely felt event, a magnitude-5.2 earthquake, was recorded by the observatory. Six days later, as the seismic activity continued, local government officials had their first meeting to discuss the possibility of a major earthquake. Over the next month, they issued four specific predictions. All were false alarms.
At 6:00 P.M. on February 3, seismic activity increased dramatically. By the next morning, when at least one earthquake was rocking the ground every few minutes, the head of the local earthquake office, Cao Xianqing, called a meeting of government officials. He stood before them and said: “A large earthquake may occur today during the day or the night.” He asked that a formal announcement be made to warn the public.
That afternoon, February 4, the government ordered all businesses and factories to close. It also suspended all public meetings and sports activities. A movie operator who, after talking to workers of the Shipengyu Observatory, was convinced that a major earthquake was imminent, decided to show movies outdoors all night to attract people away from their houses. Other people, concerned about the continued ground shaking, left their homes and prepared to sleep outside, even though it was midwinter.
At 7:36 P.M. a magnitude-7.0 event, comparable to the San Fernando earthquake, shook the ground. Most of the buildings of Haicheng and in the surrounding communities collapsed. More than 2,000 bridges were damaged. Hundreds of breaks occurred along gas pipelines. Yet, considering the severity of the event, the number of fatalities was extremely low. Some investigators, after viewing the destruction, guessed that the death toll could have been as high as 150,000, but the actual number was barely 2,000. By comparison, the same night, 6,578 people were treated for frostbite and 372 died from freezing.
So the question is: Did Chinese officials actually predict the earthquake that led to the evacuations? The answer is: maybe.
It has never been clear what the workers at Shipengyu Observatory told the movie operator that made him show movies outdoors, hoping to keep people out of their houses. Nor is it known whether those same observatory workers were ever told that Cao Xianqing thought a major earthquake was possible.
Xianqing has been interviewed several times and he confirms that, hours before the event, he did say repeatedly to a few colleagues at the government earthquake office—not Shipengyu Observatory—that a major earthquake would occur before 8:00 P.M. on the night of February 4. But why did he make such a prediction? When pressed, he answered that he knew of a book, printed in the 18th century, that said, “Excessive autumn rain will surely be followed by a winter earthquake.” The previous autumn had been exceptionally rainy, and according to the Chinese calendar, February 4 was the last day of winter. An earthquake swarm did begin on the evening of February 3, and when he made his first prediction the next morning, earthquakes were being felt every few minutes.
Also, some large towns were evacuated, such as Dashiqiao, where, out of a population of about 72,000, only 21 people died, though two-thirds of the buildings collapsed. Who ordered the evacuation of Dashiqiao remains unclear.
After the earthquake, several possible precursors were identified. The land around Haicheng had risen slowly as much as two inches since the summer of 1973. There were changes in the level of local water wells and in the color of water in those wells. The rate of emission of radon gas increased. And there was anomalous animal behavior. Of the last, the most noted was the appearance of snakes that should have been in hibernation; however, snakes first appeared about 24 hours before the main earthquake, as soon as the lesser shaking began on February 3, so seismic activity had already started before the snakes were seen.
Nevertheless, the prediction of the 1975 Haicheng earthquake was—and still is—touted as successful. It caught the attention of Frank Press and others, in part because for more than a decade scientists in the Soviet Union had been claiming that they, too, knew how to predict earthquakes.
The strategy followed by Soviet scientists was completely different from that taken by scientists in China. In the Soviet Union, earthquake prediction was based on precise measurements. In particular, Soviet scientists had noticed that the speed of seismic waves slowed down when passing through a region where a large earthquake later occurred. And there was laboratory evidence and a theory to support it.
When a rock sample is squeezed in a vise in a laboratory, tiny cracks form close to the line where a fracture eventually develops. If one taps the sample with a hammer, the speed of the disturbance produced by the hammer traveling through the sample is slowed by the tiny cracks. The same thing happ
ens, so it was argued, in nature. When two tectonic plates slide against each other, tiny cracks form in the Earth’s crust and, eventually, a large fracture—an earthquake—occurs. The presence of those cracks explains the slowing of seismic waves before an earthquake observed by Soviet scientists.
Furthermore, the formation of tiny cracks in a laboratory sample causes the sample to expand, or dilate, slightly. That could explain why the ground surface rose two inches a year or so before the 1975 Haicheng earthquake—and why, as reported by Japanese scientists, sections of the coastline have risen a few inches before at least some major earthquakes, such as the magnitude-7.5 earthquake near Niigata in 1964.
It all seemed to fit together. Laboratory tests could explain why Chinese and Soviet scientists could predict earthquakes, and there was a theory—dilatancy theory—that supported the claims. By the mid-1970s, the routine prediction of earthquakes seemed to be possible in the near future—perhaps, as some scientists including Frank Press said, as soon as five years.
Los Angeles was now the third largest city in the nation. It was only a matter of time, Frank Press and others realized, until some truly colossal event—similar to the 1857 earthquake—was unleashed along the San Andreas, an event that would be many times more powerful and more destructive than the 1971 San Fernando earthquake. Given the reported successes in China and the Soviet Union, it should be possible to recognize a sign that such a catastrophic event was imminent. Surprisingly, such a sign came sooner rather than later.
In the aftermath of the 1971 earthquake, scientists combed through measurements of land surveys to see if there was any evidence that the ground surface had moved in some systematic way before the earthquake. No evidence was found. But something more intriguing was uncovered.
Since 1960, it seemed that a broad region, more than 4,000 square miles in extent, had risen, centered on the San Andreas Fault. The maximum uplift was ten inches near Palmdale, so this broad uplift soon became known as the Palmdale bulge.
In April 1976, at a scientific meeting held in Washington, D.C., Press gave an address entitled “A Tale of Two Cities.” In it, he reminded his audience that a year earlier Chinese scientists had accurately predicted an earthquake, in part because they had recognized a broad uplift of the land around Haicheng city. Now a similar bulge had been found along a stretch of the San Andreas Fault north of Los Angeles. This “worrisome uplift,” as he called it, might or might not be a sign of an impending disaster, but “precautionary measures will not be in vain.” And he added, “The San Andreas Fault will undoubtedly rupture again.”
Later at the same meeting, a young researcher from the Seismological Laboratory in Pasadena, James Whitcomb, gave a paper in which he reported that he had uncovered a slowing of seismic waves that passed through the San Andreas Fault north of Los Angeles. Three years earlier, in November 1973, Whitcomb had found a similar slowing of seismic waves east of Los Angeles near Riverside and from that had predicted a magnitude-5.5 or greater event within three months. A magnitude-4.1 earthquake did occur in the designated area on January 30, 1974. Now, in April 1976, on the basis of the experience in the Soviet Union, he expected a magnitude-5.5 to -6.5 earthquake north of Los Angeles during the next 12 months.
The Los Angeles Times interviewed Whitcomb repeatedly, explained the dilatancy theory, and gave advice on how people should prepare themselves for the coming earthquake. A city councilman in Los Angeles threatened to sue Whitcomb for hurting property values in the city. The San Francisco Chronicle joined the Times in publishing editorials supporting a federally funded prediction program.
But by summer, the optimism started to wane.
On July 28, 1976, a magnitude-7.6 earthquake struck the city of Tangshan, 200 miles southeast of Haicheng, killing 650,000 people. It was the greatest earthquake disaster of the 20th century. No broad region of uplift or slowing of seismic waves was noticed before the earthquake. It brought into question whether the Haicheng example had been a fluke. Clearly, the prediction program in China was not reliable enough to prevent future disasters.
Thus there was more pulling back of earthquake prediction.
Whitcomb continued to analyze the speeds of seismic waves that passed through southern California, coming to the conclusion that they did not follow the pattern required by the dilatancy theory. In December 1976, he publicly withdrew the prediction.
Meanwhile, additional surveys across the region of the Palmdale bulge showed curious movements. The bulge was rising in places, while dropping in others, without any relation to seismic activity. By 1979, most of the bulge had disappeared, giving rise to questions about whether the bulge ever existed, and whether the original claim of a broad uplift might have been due to subtle measurement errors.
But back in 1976, there was real concern that the bulge was a harbinger of a major earthquake that would devastate Los Angeles. On January 14, 1976, Press gave a presentation at the White House to administration officials. As if to emphasize what could happen to Los Angeles, three weeks later an earthquake rocked Guatemala, killing 23,000. Now that something had happened in America’s own hemisphere, political wheels were set in motion toward starting a national program of earthquake research. The final assurance that the program would be realized came in March 1977 when the new president, Jimmy Carter, named Frank Press to be his science advisor.
The Earthquake Hazards Reduction Act was passed unanimously by the Senate and by a small majority in the House and became law in October 1977. Overnight, the amount of money available for earthquake research in the United States tripled. The main purpose of the act, however, was not to predict earthquakes but to reduce the impact of future ones. In that regard the program was a success, advancing engineering studies of the effects of strong seismic shaking on buildings and bridges, identifying previously unrecognized fault strands, examining the history of the San Andreas Fault and many related topics. But the prediction of earthquakes was definitely in the background until 1982, when the program was up for renewal and members of Congress wondered what had happened to earthquake prediction.
Senator Harrison Schmitt, a former astronaut and the only scientist to land on the moon, conducted hearings to determine if sufficient progress had been made under the Earthquake Hazards Reduction Act to predict earthquakes. After hearing from several experts, including Frank Press, the Senator decided there had not. He threatened to terminate the entire program unless an “earthquake prediction system” was in place somewhere in the United States “within four or five years.”
There was a rush to decide where such a system might be located. Where in the United States was a major earthquake most likely to occur within the next few years? A consensus grew: The most likely place was along a middle strand of the San Andreas Fault at Parkfield, California.
The San Andreas Fault can be divided into three main segments. The northern segment runs from Cape Mendocino to San Juan Bautista—the part of the fault that ruptured in 1906. The southern segment begins around Cholame, just north of Carrizo Plain, and runs south, eventually forming the southern boundary of the Mojave Desert, continues through Cajon Pass and San Gregorio Pass, can be picked up 20 miles east of Palm Springs in Coachella Valley, and ends at Bombay Beach on the east side of the Salton Sea. The northern half of the southern segment—from Cholame to Cajon Pass—ruptured in 1857; the southern half of the southern segment—from San Gregorio Pass to Bombay Beach—did so in about 1690. So all of the San Andreas Fault has broken during a major earthquake in the last few hundred years except for a short middle segment that runs from San Juan Bautista to Cholame and includes the ranching community of Parkfield. This 150-mile segment of the San Andreas Fault is distinctly different from the other parts of the fault: Here the fault is slowly and continuously sliding.
Ten miles south of San Juan Bautista is DeRose Vineyards. It is a family-owned business where the winemaking and tasting room is located in a large building with
a concrete floor and metal walls and roof. On the day I visited, I identified myself as an earthquake tourist. The person who was pouring the wine pointed immediately to the center of the building and said, “It’s over there.”
Here the trace of the San Andreas Fault is all too apparent. Running along the floor is a line of broken concrete slabs, up to a foot across, that extends the full length of the building. Where the fault runs beneath a metal wall, the wall has been sheared apart, the two halves now standing as much as two feet apart. Broken ends of twisted rebar are exposed where the metal wall once connected to the concrete floor. A plaque attached to a wall in the center of the DeRose Winery building proclaims the San Andreas Fault at this spot to be a registered natural landmark.
If one drives south of DeRose Vineyards, one can find sets of cracks running diagonally across the pavement. These, too, are the San Andreas Fault. They are visible, as is the slow destruction of the winery at DeRose Vineyards, because along this segment the fault is always sliding. And the sliding can be found as far south as Parkfield, where the fault runs under a bridge. As one might expect, the bridge has a distinct bend over the exact place where it crosses the San Andreas Fault.
The slow sliding is known as seismic creep, caused in part by a constant jitter of small earthquakes. At DeRose Vineyards, the fault slides about an inch a year. At Parkfield, it is half that amount, which means occasionally the Parkfield section has to catch up. It does so with a jolt—a moderate earthquake.
Six times—in 1857, 1881, 1901, 1922, 1934, and 1966—the Parkfield section has surged forward. Each event has been nearly identical in size—corresponding to a magnitude-6 earthquake—and each successive event has occurred, on average, 22 years after the previous one. Moreover, there seemed to be definite precursory signs before the last two events. The main shocks in 1934 and again in 1966 were preceded 17 minutes by a strong foreshock that was felt over a wide area. Furthermore, an irrigation pipe that crossed the rupture zone separated nine hours before the 1966 event. All this gave credence to the idea that the next Parkfield earthquake might be predicted.
