A Correlation Between Nuclear Explosions And Earthquakes?

Press, Volume CX, Issue 32386, 27 August 1970, Page 19

A Correlation Between Nuclear Explosions And Earthquakes?

(By

PEARCE WRIGHT.

r. of "The

Times,” through N.Z.P.A.)

LONDON. Last July’s Persian earthquake disaster, coming two days after a French H-bomb test, is bound to be taken as further evidence by those who see an unnerving correlation between nuclear explosions and seismic upheavals.

These fears are not just ronfined to anxious old ladies who are prepared to blame bomb-testing for any persistent bout of unwelcome weather.

For some months now there has been a battle of statistics in progress in scientific journals between two groups of American scientists who have been investigating this suspected relationship. The arguments are complicated technical ones, but they are additionally involved by the inherently-emotional content of the subject Unhappily, the first six months of this year saw a series of events which rank with the major natural disasters to be recorded. They also occurred at a tim e that on superficial examination provides a damaging indictment against the testers. There i s gn earthquake of some sort every day of the Fear. As they tend to take Place in some of the remoter Parts of the globe, they do not often exact a heavy toll on life and. therefore, are recorded more for scientific knowledge by the seismolo--Bists and geophysicists. It happens that an unprecedented number of deaths has been caused this year in earthquakes that all took Place within two and three days of nuclear tests. These were:

March— United states test. Earthquake in Turkey, 1080 killed.

May—French test EarthIn Peru - 50 ’ 000

July—French test. Earthquake in Persia. The first two of these disturbances have been officially recorded in the international library of the Smithsonian Institution for short-lived phenomena as earthquakes with magnitudes greater than force 7 on the Richter scale. This is the scale devised to convert the readings from seismometer instruments into measurements of the enormous energy released. The power of the forces at work is unimaginable, and involves energies of about 1000 megatons compared with a trifling few megatons of a man-made H-bomb. There have been equallylarge events recorded in sparsely-populated regions

this year. What evidence exists to implicate nuclear testing as the cause of destruction?

Analyses of seismic records that might establish or disprove a connection between the natural and manmade disturbances were started in the United States two years ago. Most of the work was influenced by the decision of the Atomic Energy Commission to move to a new testing site in the Aleutian Islands. Unlike the mode-rately-passive experimental ranges of the Nevada desert, the new location is in a rocky, seismologically-active region. It lies close to one of the earthquake-prone belts that form an untidy and interlinked pattern beneath the surface of the earth. Several scientists expressed concern about moving into an unsettled region. Evidence to show a connection between earthquakes and nuclear devices was provided by a group at the School of Mines of Nevada University. Their analysis was of seismic disturbances recorded at two stations after two particularly-large explosions called “Faultless” and “Boxcar” in Nevada early in 1968. They found that several shocks occurred up to two to three days after the teste, and that small tremors took place for several weeks afterwards. A later study by Professor C. Emiliani, of Miami Uni- ; versity, suggested that the i induced activity could spread as much as 500 miles from i the testing centre in Nevada. I Part of the problem in . reaching some sort of conclu- , sion lies in the fact that little ] is known about processes pre- , ceding earthquakes and ' methods for predicting an . upheaval are still being ’ developed. One theory is that ' a large earthquake can be ’ triggered off by a distant ’ event of much smaller magnitude. ! But it would need a very - refined means of statistical ■ analysis to be able to show i a relationship between the s natural and artificial circumstances. It would be akin—-

but much more difficult to perfect—to the statistical techniques of the epidemiologists for investigating the patterns of diseases. There would be some similarity with the way the incidence of lung cancer in smokers was ultimately picked out from the mass of information of likely causes of the disease.

But Dr P. A. Mohr, of the Smithsonian Institution, showed that the process of triggering earthquakes from a primary natural disturbance was very much on the cards. His investigation was one of the studies in ways of devising methods of prediction, not an investigation of the nuclear aspect. However, he proposed a domino theory on the evidence of a succession of earthquakes in the Middle East at the beginning of last year.

If scientific detachment can be applied to an examination of a process which might have caused the loss of 50,000 lives, then there does

seem to be a need for impartial research. Early last July, the findings of Professor Emiliani were challenged by two scientists of the United States National Centre for Earthquake Research. They have been scrutinising the original work that covered a five-year period in which there were 170 bomb tests and more than 1000 earthquakes in the area under study. Professor Emiliani found a higher incident of tremors after testing. Extending the period from five to seven years, his opponents show that the statistical imbalance between earthquakes before and after disappears. These two scientists, Dr J. H. Healy and Dr P. A. Marshall, conclude that statistics are not enough.

What is needed is a physical theory of the relationships between explosions and earthquakes, which they suggested (rather alarmingly) can be checked against observation.