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Fascinated by the implications of what were apparently man-made quakes, USGS scientists in 1969 set up their instruments at the Rangely oilfield in northwestern Colorado. There, Chevron was recovering oil from less productive wells by injecting water into them under great pressure. The recovery technique was setting off small quakes, the strongest near wells subjected to the greatest water pressure. If water was pumped out of the earth, the survey scientists wondered, would the quakes stop? In November 1972, they forced water into four of the Chevron wells. A series of minor quakes soon began, and did not stop until March 1973. Then the scientists pumped water out of the wells, reducing fluid pressure in the rock below. Almost immediately, earthquake activity ended. In a limited way, they had controlled an earthquake.
The results of the Rangely experiments led USGS Geophysicists Raleigh and James Dietrich to propose an ingenious scheme. They suggested drilling a row of three deep holes about 500 yds. apart, along a potentially dangerous fault. By pumping water out of the outer holes, they figured they could effectively strengthen the surrounding rock and lock the fault at each of those places. Then they would inject water into the middle hole, increasing fluid pressure in the nearby rocks and weakening them to the point of failure. A minor quake—contained between the locked areas—should result, relieving the dangerous stresses in the immediate vicinity. By repeating the procedure, the scientists could eventually relieve strains over a wide area. Other scientists feel that such experiments should be undertaken with caution, lest they trigger a large quake. Raleigh is more hopeful. In theory, he says, relatively continuous movement over the entire length of the San Andreas Fault could be maintained—and major earthquakes prevented—with a system of some 500 three-mile-deep holes evenly spaced along the fault. Estimated cost of the gigantic project: $1-$2 billion.
In a time of austerity, the possibility of such lavish financing is remote. As M.I.T.'s Press puts it: "How does one sell preventive medicine for a future affliction to Government agencies beleaguered with current illness?" Ironically, the one event that would release money for the study of earthquake prediction and control is the very disaster that scientists are trying to avert: a major quake striking a highly populated area without any warning. Tens of thousands of people living in the flood plain of the Van Norman Dam had a close call four years ago in the San Fernando Valley quake; had the tremor lasted a few more seconds, the dam might have given way. When the San Andreas Fault convulses again—as it surely must—or when another, less notorious fault elsewhere in the U.S. suddenly gives way, thousands of other Americans may not be so lucky.
* Used to measure the strength of earthquakes. Because the scale is logarithmic, each higher number represents a tenfold increase in the magnitude of the tremors, and a 30-fold increase in the energy released. Thus a 2-point quake is barely perceptible, a 5 may cause minor damage, a 7 is severe, and an 8 is a violent quake.
* U.S. scientists now estimate that the change can occur as long as ten years before a magnitude 8 quake, a year before a 7-pointer and a few months before a magnitude 6.