Word: tremoring
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Champagne flowed at a rate that rivaled that of the Olympus engines' fuel consumption. At mach 2 (1,320 m.p.h.) which we passed without a tremor, came the food-smoked salmon, rib of veal, château potatoes, cheese, apricot pastry, Chablis Vaudésir and Château Haut-Brion, plus liqueurs. Many passengers paid the smoothness of supersonic flight the ultimate compliment; they fell asleep. We touched down in Dakar, West Africa, right on schedule, refueled and were on our way to Rio in an hour. A minor engine problem held our speed below mach...
...most important signal, they said, was a change in the velocity of vibrations that pass through the earth's crust as a result of such disturbances as quakes, mining blasts or underground nuclear tests. Earth scientists have long known that tremors spread outward in two different types of seismic waves. P waves cause any rock in their path to compress and then expand in the same direction as the waves are traveling. S waves move the rock in a direction that is perpendicular to their path. Because P waves travel faster than S waves, they reach seismographs first...
...search of past records, they found a distinct drop in the speed of P waves 3½ years before the 1971 San Fernando quake (58 deaths), the largest in California in recent years. The P waves had returned to their normal velocity a few months before the tremor. Besides providing what amounted to a retroactive prediction of that powerful quake, the Caltech researchers demonstrated that it was primarily the velocity of the P waves, not the S waves, that changed. Their figures were significant for another reason: the P-wave velocity change was not caused by a quirk of geology...
...earth rumbled under his feet. "I could feel the waves passing by," he recalls, "and I was jubilant." In November 1973, after observing changes in P-wave velocity, Caltech's Whitcomb predicted that there would be a shock near Riverside, Calif., within three months. Sure enough, a tremor did hit before his deadline-on Jan. 30. Whitcomb's successful prediction was particularly important. All previous forecasts had involved quakes along thrust faults, where rock on one side of a fault is pushing against rock on the other. The Riverside quake took place on a strike-slip fault, along...
...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...