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Small Displacements: Laser technology is applicable also to earthquake prediction. Current efforts in California, for example, include precise measurements of small displacements of the crust along major faults. Such displacements occur prior to the actual advent of large earthquakes, and stationary laser stations—that remain in a fixed position during the displacements—on both sides of the fault would have an interesting story to tell.
A further use of gyroscopes is found in their employment as stabilizers, as on aircraft and ships, to keep inertial guidance systems steady despite the sometimes violent motions of the vehicles. In such cases the gyroscope is made very large and given a large amount of angular momentum. The rate of precession will then be very small, since the precession is inversely proportional to the angular momentum; this small rate of precession means that the system resists angular displacements.
All attempts at earthquake prediction involve the correct interpretation of signals preceding the event. These signals, in addition to those provided by small displacements along faults, include certain changes in the nearby rocks. Changes in strain patterns, magnetization, and other physical properties of the rocks, and changes in the frequency of occurrence of micro-shocks (very small earthquakes that occur all the time) all are clues for impending quakes. If scientists can determine which of these signals are consistently associated with earthquakes, and the size of certain signals just prior to the quake, then earthquake prediction can be more soundly based than it has been in the past.
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