Shock Warning: The Race to Predict Earthquakes

Shock Warning: The Race to Predict Earthquakes

By Mr Ghaz, February 15, 2010

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Shock Warning: The Race to Predict Earthquakes

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A YEAR SELDOM PASSES that an earthquake does not strike somewhere in the world, leaving death and destruction in its wake. Casualties can number in the thousands, and the damage to property is sometimes in the millions of dollars. Those living in an earthquake zone realize that it is only a matter of time; sooner or later it will be their turn to experience one.

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Scientists know where future earthquakes are likely to occur: usually at those points on the earth’s surface where the crustal plates meet. The west coasts of North and South America parts of the Mediterranean, and the Pacific coast of Asia are the world’s earthquake hot spots. Earthquakes often shake the same place twice-or three or four times. For example, the Portuguese capital, Lisbon, has been struck in 1344, 1531, and 1755. The last earthquakes almost completely destroyed the city; the next one is overdue.

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San Francisco is another city anticipating the worst. The last earthquake, in 1906, claimed well over 700 lives and started a fire that swept through the city. The next quake may be even more severe. The U.S. Geological Survey estimates 3,000 deaths-even 11,000, depending on the time of day. And it could happen soon, which is one of the reasons the race is on to discover a method of predicting earthquakes with much greater accuracy so that measures can be taken to minimize danger.

Taking the Earth’s Pulse

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San Francisco lies close to the San Andreas Fault, one of the strongest areas of seismological activity on the earth and an area that has been more closely observed than any other in the United States. Small tremors that occur almost every day are plotted by scientists trying to identify a pattern of activity.

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One team is using laser technology to detect the smallest movements. A laser beam is reflected off mirrors on either side of the fault; small changes in the direction of its reflection indicate that the earth under the laser itself has moved a tiny fraction of an inch. The seismographic equipment that picks up tremors is so sensitive that nearby traffic can create serious problems; the vibration of automobiles has to be screened out in order to record the earth’s own movements.

Success…and then Disaster

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On February 4, 1975, in the province of Liaoning in northeastern China, authorities predicted an earth-quake and ordered the evacuation of major cities in the earthquake zone. More than a million people poured into the open areas in and around these urban sites. That same afternoon a severe tremor hit the city of Haicheng, and 90 percent of its buildings were damaged or destroyed. The decision to evacuate had saved the lives of an estimated 10,000 people.

The accuracy of the prediction was totally unprecedented. Chinese scientists had based it on their observations of geological activity but had taken into account other, less technical phenomena. They had heeded reports of unusual animal activity-chickens roosting high in trees, fish leaping in rivers, and snakes leaving their burrows.

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The accuracy of the Haicheng prediction was impressive, but a little more than a year later, the unpredictability of earthquakes reasserted itself. On July 28, 1976, as Chinese scientists were meeting to discuss signs of an impending earthquake in the city of Tang Shan, some 120 miles east of Peking, disaster struck. A massive shock hit the city, leaving nearly a quarter of a million dead, the worst toll recorded in modern times.

A Pattern

Both natural and technological observations have failed to predict earthquakes reliably. But recently scientists have uncovered a surprising fact.

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From the records, it appears that earthquakes occurring in the same place happen with remarkable regularity. The small community of Parkfield, located between San Francisco and Los Angeles, has experienced an earthquake almost every 22 years.

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The next one is due and seismologists have moved in to study the phenomenon at first hand. The area is under detailed scrutiny by sensitive seismographs and the laser measuring system. If the earthquake hits, it will help confirm that the regularity theory offers a scientific basis for earthquake prediction.