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| Awareness of earthquake hazards is now
well developed in many countries, and the U. S. Geological Survey has recently
published a map showing the relative probability of earthquake activity for
various areas in the United States. The major hazard represented by seismic events along the great earthquake belts of the world has now been clearly recognized, and a great deal of research money and effort is being directed toward earthquake prediction and possible control. Active fault systems, such as the San Andreas fault in California, are carefully monitored for observable changes that could indicate an impending earthquake. Although the nature of earthquakes and earthquake belts are rela tively well understood, the possibility of accurately predicting major earthquakes, much less controlling them, still appears remote. Probably the most intriguing development in this field relates to the Rocky Mountain Arsenal earthquakes near Denver, Colorado. In 1962 injection of fluid wastes into the Precambrian basement rocks nearly 4000m below the ground surface was followed by a series of small earthquakes. Studies of this phenomenon have indicated that the injected fluid lubricated a fault zone under stress and thereby promoted release of seismic energy. Experimentation at the site is still going on, but the connection between the fluid injection and earthquake activity was quickly rea lized. Accordingly, the suggestion has been made that potentially destructive earthquakes could be converted into numerous nondestructive minor earthquakes by using fluid injection techniques. Thus, although man has no hope whatever of controlling the major earth movements that lead to earthquakes, he may in some cases be able to influence the manner in which earthquake energy is dissipated. |