The Taming of Earthquakes

Japanese mythology once held that earthquakes were caused by movements of a great spider that carried the earth on its back. Mongolians blamed earth tremors on the unsteady support of a giant hog. Early seismologists assumed that the chronic buckling and lunging of the earth's surface was the result of the globe's slow cooling and contraction. Now new instruments and theories are changing what was once a guessing game into precise science. Some seismologists are even saying that accurate prediction of earthquakes is only three to five years away, and that control of quakes may be just beyond that.

The key to this optimism is the upheaval in geological thinking that took place during the 1960s. No longer is the earth's crust thought of as a rigid shell, but rather as a dozen gigantic, mobile "plates." These plates are thought to be driven slowly across the terrestrial surface by enormous currents within the earth. When two plates collide, one slides under the other, causing deep and devastating earthquakes like the one that rocked Peru in June. Shallower quakes occur when two plates slide past each other, as do the two sides of the San Andreas Fault system in California.

Seismic Symphony. The California legislature has released a progress report by its Joint Committee on Seismic Safety that includes a stark scenario describing the effect in 1970 of an upheaval as great as the 1906 San Francisco earthquake--an event to be expected every 60 to 100 years. Water mains would burst, elevators stop and power lines topple. At least one of the area's 228 dams and reservoirs would give way. Countless Bay Area buildings would sink into the shifting alluvial soils on which they have carelessly been built; such soil can turn into quicksand during a quake. The entire region would be cut off from outside aid, as freeways, bridges and runways buckled and railway tracks twisted. Deaths would reach the hundreds--some say tens of thousands--and property damage some $30 billion.

This specter and the two huge earthquakes of 1964 in Alaska and Niigata, Japan, have recently resulted in new funds for research facilities and grants to study the million quakes a year that produce the world's seismic symphony.* Understandably, the U.S. is concentrating its efforts on quivering California, where both the Environmental Science Services Administration and the U.S. Geological Survey have new laboratories.

At the Geological Survey's lab at Menlo Park, a fired-up corps of young scientists is "bugging" central California's creaking faults with ultrasensitive new instruments. The lab has already set up more than 100 seismic stations, one-eighth of the world's total, to detect ever smaller earth tremors.

"This enables us to use small earthquakes to paint in the boundaries of the blocks of the earth that are moving," says Menlo Park's Jack Healy. Scientists are also studying the minute tilting of the ground that may precede quakes and the slow fault "creep" of those parts of the San Andreas that are moving freely. They are measuring the minute warping of rock along "locked" areas, changes that reflect the gigantic, subterranean forces urging that part of California west of the fault to move toward Alaska. In addition, the electrical and magnetic properties of rocks have been found to depend upon the amount of strain the rocks are undergoing. Predicts Jerry Eaton, Menlo Park's chief scientist: "We will be able to put all our clues together pretty soon and make short-term predictions on the order of days or hours."

Many engineers argue that because quakes are here to stay, the best approach is not predicting them but erecting sound buildings, bridges and dams on relatively safe sites. "It's not earthquakes that kill people," says Don Tocher of the new ESSA lab, "it's the buildings that people build that kill people." But seismologists point out that high costs have discouraged the construction of better buildings.

Locked Faults. There is one ideal solution: earthquake prevention. Some scientists have proposed using H-bombs to jar loose locked sections of faults, thus relieving accumulating strain that would otherwise build up to dangerous levels. More realistic is the possibility of using pressurized water or liquid waste to release this pent-up seismic energy. At two carefully studied sites in Colorado, liquid injections have been found to "lubricate" locked fault systems. This allows the plates to resume sliding past each other, setting off small but relatively harmless energy-dissipating tremors.

Before putting earthquake controls into practice, seismologists are striving to perfect their predicting techniques. They are making progress. In June, Menlo Park scientists correctly assured worried county officials that a "swarm" of hundreds of small tremors near San Francisco would not threaten the city. The Japanese have made successful forecasts days and weeks in advance. One measure of their accuracy was the unhappiness caused among members of the hotel and sightseeing industries at Matsushiro in 1967, when seismologists accurately predicted that a small swarm would be followed by a series of larger tremors. Such predictions, the merchants complained, were bad for business.

* During the past century, U.S. quakes alone have killed more than 1,500 people and caused $1.3 billion worth of property damage. Last year 303 tremors were felt in 22 states.

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