Are we wobbling to disaster?

Press, 25 February 1981, Page 21

Are we wobbling to disaster?

By

BRUCE SANDHAM

Features International

To the astonishment and alarm of the world’s scientists,' the earth’s axis has, for the last few months, been jerking backwards -and forwards around the geographical North Pole at the rate of about six inches a day. • This might not sound a lot In fact it means that the earth is wobbling as it spins in space — a wobble that will continue to increase as it reaches the peak of its 10year cycle in the middle of this year. Scientists blame the wobble for the increasing num‘ber of serious earthquakes in the last five years, and warn that there could be worse to come this year. Historically, there is ample backing for their fears: during the two previous peak periods, 11,000 earthquake victims died in Iran and thousands more were killed in major tremors in Alaska, Turkey, Greece, Brazil, Algeria and the Philippines. Since 1976, when the present wobble started to gain momentum,, there have been nearly a dozen major earthquakes, culminating in last autumn’s Italian disaster. Where the next big ’quake will be is anyone’s guess, but experts are looking towards the North American continent where, just over a year ago, an ominous tremor rocked San Francisco, scene of the epic disaster of 1906. Now a series of seismic stations check every mile of California’s 1000-mile San Andreas Fault,- measuring earth movements to the millimetre with the aid of lasers. Quake-prone countries like Japan, China, America and Russia are using space satellites to measure the rock changes that invariably herald a major earth movement No longer can the coupling of excessive earth-wobble and serious earthquake damage be regarded as coincidence, according to such distinguished experts as Dr Charles Whitten, Chief Geologist of America’s National Ocean Survey, who has prepared a graph showing the connection between earthquakes of the'last few years and the daily movement of the pole. As a result he claims, there seems no doubt that major earthquakes coincide with maximum earth wobble. "The correlation between the total earthquake energy

release and the daily movement of the pole is so strong at the moment that I intend to keep a very close watch over the next few months,” says Dr Whitten. The reason for the wobble is still ‘ largely a mystery. Some scientists believe that the sloshing of the world’s molten core against the planet’s otherwise rigid structure has something to do with it Others think it is due to the . melting ice-caps, the

movement of the seas, or the unbalancing effect of the .world’s land masses.

•Whatever-the reason, there are about a million tremors a year when — as at the moment — the wobble is at its worst, particularly in two belts which stretch around the world.

One takes in the east coast of Asia and the West Coast of America. The other stretches

across the Mediterranean to Iran and Burma. As the earth’s wobble has gathered momentum, these areas have suffered the brunt of recent major earthquake disasters. In July, 1976, for

example, 750,000 people died in Tangshan, China, followed ■ by 1500 in Rumania in March, 1977. There were a further 25,000 victims in Iran the following year, and 22,000 in Guatemala. More than 2500 people died in October, 1980, when an earthquake struck El Asnam, Algeria, leaving a further 100,000 homeless. In all these areas, geologists are now hard at work trying to discover ways of

making buildings and their occupants less vulnerable to the earthquakes they fear could arrive in the coming months.

To do this, they iriust discover exactly what happens to a building when it is hit by an earthquake. Why do some stay up while others, apparently similar, fall down?

Devices known as accelerographs and seismoscopes are helping to find out. When installed in buildings and other structures, they can “freeze” earthquake motion in such a way that engineers can then duplicate it in computers to test the reaction in other types of structure. The results of some of the latest findings are already being incorporated in the building codes of over a dozen nations. Research has shown that the real damage in an earthquake is caused by the sideways movement Until recently it was thought that this sideways force on buildings hit by an earthquake would be no more than a third of the force of gravity. But recent measurements have shown that it may even exceed the force of gravity by a quarter. A complication is that earthquake waves are sometimes deflected by bodies ofrock underground so that even a sophisticated computer programme cannot predict all the effects. This, it is hoped, is being remedied by the latest studies and research. Using ul-tra-sensitive devices, electronics scientists can now measure vibrations in buildings by “sounding” them in a way similar to a doctor listening to a patient’s heartbeat.

This way they can detect faults that an ordinary survey would almost certainly fail to find.

Other experts are investigating the relationship between earthquake damage and the type of rock and soil found beneath a building’s foundations. Some soil, they believe, allows tremors to pass through it more easily, thus causing more damage. All this research is being carried out with a deep sense of urgency. For every month that passes brings nearer the time when the world will once aggjjj wobble its way to