Earthquake Alert! What Should You Do?
DURING the year 1976 alone it is possible that over 686,800 persons lost their lives as a result of earthquake activity world wide. Thousands of others suffered the loss of material possessions, including their homes. Indeed, when these mighty temblors strike—possessions, life and limb all are imperiled.
Moderate earthquakes register 6.0 to 6.9 on the Richter scale. Major temblors have a Richter rating of 7.0 to 7.9, and giant quakes are those registering 8.0 or greater. Guatemala, the Panama-Colombia border, the Kuriles, Sumatra, New Guinea and Turkey each had a major quake; the Soviet Union had two and China three. Two giant quakes struck the Kermadec Islands in the South Pacific, and one hit Mindanao in the Philippines. And this was not all the earthquake activity world wide during the months of 1976.
Since quakes can be so dangerous and death-dealing, what would you do if you heard a broadcast warning that there would be a destructive earthquake in your locality within the next day or two? But can scientists really predict earthquakes? How seriously, for example, should people living in southern California take the recently publicized warnings that a dangerous bulge has been developing in that area?
Beginnings of Earthquake Prediction
A few earthquakes already have been correctly predicted. One of the first successful forecasts was made by Dr. James H. Whitcomb, a geophysicist at the California Institute of Technology. In December 1973 he predicted that within three months an earthquake would occur east of Riverside, California, and that it would have a magnitude of 5.5 or more on the Richter scale. As predicted, a tremor was recorded on the following January 30, centered about 30 miles (48 kilometers) east of Riverside. However, it read only 4.1 on the Richter scale.
Later that year, at an informal gathering of geologists in northern California on the evening of November 27, scientists of the Menlo Park laboratory of the United States Geological Survey said that a quake of about magnitude 5 was to be expected on the San Andreas Fault near Hollister, possibly the next day. The very next afternoon, Hollister was shaken by a tremor of Richter rating 5.2.
By far the most striking earthquake forecast till now was reported from China. On February 4, 1975, Haich’eng, in Liaoning Province in northeast China, was hit by a strong earthquake of magnitude 7.3. The city was destroyed, but there was little loss of life because seismologists had foreseen the quake and the people had been alerted to the danger. A general evacuation had been ordered and a million persons in the area left their houses. Barely five and a half hours after the final warning, the destructive shock struck. Though thousands of houses were destroyed, only some 200 persons were killed.
Learning of the timely Chinese warning, people in other areas subject to earthquakes wonder why such forecast service cannot be provided there also. What signs enable seismologists to say that an earthquake is imminent? What kind of instruments do they use? How much would people be willing to disrupt their routine of life in response to earthquake alerts? And what would be the effects of false alarms?
Preliminary Movements of the Crust
For one thing, to predict a quake geologists watch for signs of deformation of the ground’s surface. It is believed that large plates of the earth’s outer crust are slowly moving over its surface. Geological “faults” exist where two plates come in contact. Where one plate juts into another, the ground may be thrust upward. On the other hand, where one plate slides past another, there may be a horizontal displacement of lines crossing the fault.
Such movements amount to only a few inches a year, and so are not obvious. However, they can be detected by accurate surveys made over a period of years. The so-called Palmdale bulge, north of Los Angeles, California, is an area of some 4,500 square miles (12,000 square kilometers) that is being uplifted. It now stands as much as 10 inches (25 centimeters) higher than it did fifteen years ago. This suggests that strain is building up that will be relieved eventually by an earthquake.
Farther north along the San Andreas Fault in California, surveys have shown for many years that the ground on the west side is inching north against the ground on the east side. In the neighborhood of the city of Hollister, this movement is effected by a more or less regular succession of small quakes along the fault. Still farther north, where the fault cuts through San Francisco, such activity is lacking. Here it seems that the two sides of the fault have been locked together since the great quake of 1906. If this is true, it leads to the ominous conclusion that when the accumulating strain reaches the limiting strength of the rocks, it will be relieved suddenly in another disastrous quake.
Ordinary surveying methods can tell the seismologist where an earthquake is liable to occur, but they can give only a rough idea as to when it will happen, or how strong it will be. Recently, the laser has been put to use for precise surveying in the Hollister area. With this, movements of “bench marks” on opposite sides of the fault can be measured much more precisely. Consequently, small movements can be detected sooner. This promises to help to sharpen the prediction of the time of quakes.
The most valuable indicators in earthquake prediction at present are based on analysis of seismograph records of small earthquakes or man-made blasts (as in rock quarries). Seismologists long have distinguished two kinds of signals in the transmission of shock waves through the earth’s mantle. One kind is called the P-wave. It travels by compression of the rock in the direction that the wave is moving. The other, called the S-wave, is transmitted by sideways compression, perpendicular to the direction of the wave. P-waves travel faster through the rock than S-waves, and so they appear first on the seismograph.
In 1971 Soviet scientists reported that they had found that the P-waves are slowed down for some time before a large earthquake. The speed is reduced beginning some weeks or months beforehand, but it suddenly returns to normal just hours or a few days before the quake. Going back over their past records, United States scientists verified this observation. In fact, they found that there had been a drop in velocity of P-waves three and a half years before the destructive quake at San Fernando, California, in 1971. This phenomenon was the basis on which the Riverside tremor of 1974 was successfully predicted.
In regions that are seismically active, usually there are frequent small quakes, of magnitude 3 or 4—so small that they are not noticeable without instruments. It has been found that these minor tremors may stop, resulting in a calm period of some months, and then resume just before a large quake. Hence, by carefully monitoring the records of seismographs installed throughout a region under surveillance, scientists may get an early warning as well as an urgent signal of a destructive earthquake.
Other Warning Signals
Other types of measurement that may be useful in predicting the times and magnitudes of earthquakes are based on laboratory studies of rocks. As a rock is put under more and more stress, it shows signs of strain long before it breaks. The rock seems to begin swelling as tiny cracks form and grow in it. This changes several properties of the rock, which can be measured, not only in the laboratory, but also in the earth’s crust. Among these effects are: (1) an increase in volume of the rock; (2) a change in its electrical resistance; (3) accompanying changes in the local magnetic field; and (4) an increase in permeability to gas or water. All of these suggest possible measurements in the field that may give precursory signals of impending earthquakes.
When the rock swells, it may shift position slightly. A tiltmeter (like a carpenter’s level, only much more sensitive) can be placed in the rock to indicate such a shift. An array of such devices spotted along the San Andreas Fault for some 53 miles (85 kilometers) gave the precursory indications on which the Hollister forecast of November 1974 chiefly was based.
The electrical resistance of rocks in a seismic region can be measured by feeding current into electrodes set in the ground several miles apart and by measuring the voltage on other electrodes. Studies in the U.S.S.R. show that a decrease in resistance may occur gradually over a period of several months before an earthquake. Sometimes the change is reversed shortly before the quake. Similarly, an instrument to measure the earth’s magnetic field to a precision of one part in a hundred thousand may indicate an impending quake by unusual readings. Magnetic changes had been seen before the Hollister tremor.
The increase in porosity of rocks before they rupture seems to fit in with the observation that more radon than normal is found in well water before a quake. Radon is a radioactive gas that is produced by traces of uranium in the rocks. When cracks develop under growing stress, more radon can escape into the ground water. Instruments to detect this emanation are extraordinarily sensitive and can be used to monitor wells throughout a seismic region.
The swelling of rock also seems to explain changes often observed in water level of wells before a quake. All that these observations require is that someone keep watch on the selected wells and report any changes. A team of amateurs in Japan claims to be able to foretell quakes by this method alone.
There have been stories that animals behave strangely just before a quake. It is said that horses become skittish, dogs run away from home, rats leave buildings and chickens will not go to roost. In the wild, squirrels and birds migrate and snakes leave their holes en masse. At zoos, monkeys panic, peacocks scream, swans leave the water, and pandas moan and dance. Such accounts are taken seriously in China and are included with the more “scientific” data in forecasting earthquakes. Some Western scientists now are becoming more inclined to study animal behavior as another possibly useful quake precursor.
Programs for Earthquake Forecasts
All in all, it appears that scientists are approaching the ability to predict earthquakes. However, it is one thing to solve the basic scientific problems involved, and it is quite another to provide earthquake forecasts to all parts of the earth where they may be wanted. Earth scientists point out that the financial support provided in the United States for research on earthquakes has been very small. And actually deploying the needed instruments over large areas will be even more expensive. Also, large staffs of scientists and technicians may be needed to watch the instruments and analyze the records.
However, suppose we have reasonably reliable earthquake predictions. What are we going to do with them? Some have worried that the prediction might throw people into such panic that the resulting damage would be as bad as that caused by the quake itself. While such fear may be exaggerated, what about false alarms? Suppose a large city suspends or curtails its normal industry and commerce for an earthquake alert, but nothing happens after a day or two and the alert is lifted. Imagine the complaints voiced over economic losses!
Some persons might even argue against warning the public about an earthquake. When Dr. Whitcomb told the newspapers that a damaging quake might hit the Los Angeles area within a year, a city councilman talked about bringing a damage suit against him because real-estate values would be depressed by his announcement.
What Would You Do?
How would you react to a credible earthquake prediction? Would you alter your routine of life to increase your chance of survival, in case the prediction proved true? What steps could you take?
You could arrange for your family to sleep in an open space. If you have camping equipment, such as a tent, sleeping bags, portable lights or a stove, you could put them to good use. If you have a car, you might leave it outside the garage, in the driveway or the street. It would be prudent to put some drinking water in containers in a secure place. Also, some canned or packaged food could be placed where it would be accessible if your dwelling collapsed. You would be wise to avoid going near or into large buildings. If you live in an individual house, do you know where the gas and electricity can be turned off, to reduce the risk of fire from broken wires and loosened pipes?
If you live where a disastrous earthquake is not unlikely, some precautions would be worth while, even if a quake struck without warning. You could keep emergency equipment and supplies where they would be accessible if your house collapsed. With your family, you could plan alternate ways of escape from your house or apartment if the usual exits were blocked. You could always keep a flashlight where it is readily available.
As Jesus Christ foretold, destructive earthquakes can be expected to continue, one place after another,” until this present “system of things” comes to its end. (Matt. 24:3, 7) In the meantime, if earthquake forecasting becomes a reality, you would be wise to take such warnings seriously. Even now, if you live in a threatened area, it is prudent to plan what you would do if a large earthquake struck without warning. The Bible says: “Shrewd is the one that has seen the calamity and proceeds to conceal himself.”—Prov. 22:3.