Following the experience with earthquakes at the Rocky Mountain Arsenal, it was recognized that there might be other places where earthquakes were triggered by fluid injection. In fact, Griggs suggested that it might be possible to control earthquakes by controlling subsurface fluid pressures. A seismic observatory at Vernal, Utah, reported many earthquakes near the Rangely oil field in northwest Colorado. The U.S. Geological Survey observed earthquakes in the field for one month in 1967 and established two active zones, both on the periphery of the field, both areas of waterflooding and high reservoir pressure.

In 1969, the U.S. Geological Survey began a four-year experiment to control earthquakes along one active fault. Through an arrangement with Chevron Oil Company, the operator of the Rangely unit, the U.S. Geological Survey gained operating control of four water-flood injection wells in one of the zones of earthquake activity. The experiment was conducted in three phases: (1) an initial phase of reducing fluid pressure, an attempt to stop the earthquakes; (2) a second phase of reinjection and increased pressure, an attempt to reactivate the fault; and (3) a fluid phase of reducing pressure, an attempt to terminate earthquake activity along the fault. The experiment was completed successfully during the summer, 1973. The results demonstrate conclusively that by controlling the effective tress through the injection and withdrawal of fluids, it was possible to control earthquakes, at least in favorable geologic environments.

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