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• OCTOBER -NOVEMBER 1995 ' his paper is an attempt. to undetsta~d distribut,ions, patterns and directio~s of large earthquakes of RIchter magnItude (M) greater than or equa~ t06 (>=6) since 1900. Secondly, attempts will be made to relate such large earthquakes to the patterns of nuclear testing. Such' testing is conducted by the United States (USA), the [former] Soviet Union (USSR), France, the United Kingdom (UK) and China. Emphasis was p'laced on earthquakes of M>=6 because these are the ones that cause con siderable property damage and/or killl hundreds of people in short perio~s of time. Further, the data was more fQanageabre when such magnitude earthquakes were consid ered. For ex.ample, there are between 5,000 to 7,000 earthq1,lakc-s of M>=4.5 each year around the world, whereas in any 'given year since 1900, the highest number of earth quakes M>=6 was 214 (in 1957). As the magnitude threshold is lowered, many thousands more small events must be screened. Earthquakes have always been part of the Earth's geologic history. On the other hand, nuclear testing only began in earnest in i 951. In 1963, such testing was moved under gmund. The greatest recorded earthquake death toll of 830,000 was in Shaanxi, China, in 1556. The worst in this cent.ury was on 28th July 1976 when the north-eastern Chinese city of Tangshan was leveIred and about 800,000 people were 'hUed. That quake mea sured M7.8. Coincidentally, five days Ibefore the quake (23rd July), tile French detorrared a nuclear bomb in the South Pacific Mururoa Atoll, and, one day before (27th Jury), the USA detonated a.nuclear Ibomb oJ 20-150 kilotons (KT) at ,the Nevada test site. The nuclear era began on 16th July 1945 when "Trinity" was dropped 100 feet from a tower near Alamogordo, New Mexico. The yield was 19 KT of TNT equivalent. Soon after this test, on 5th and 9t.b August, the .15-KT nuclear device, "Little Boy", was dropped on Hiroshima, and the 21-KT "Fat Man" was dropped on Nagasaki, endjng World War II. Since 1945, the major powers have cxploded a total of over 1,800 nuclear bombs (through March 1'989). An average of close to 50 underground nuclear tests have taken place each year since 1980. There is little doubt that planet Earth is under severe environ mental stress. It is not getting any better. Recently the prestigious env,ironmental research group, the Worldwatch Institute, issued their latest State of the World report which shows that the world is being pushed to the brink. "We are losing at this point, clearly losing the battle to save the planet," said the report's chief author, Lester Brown. The impending result, he warned, "will shake the world to its foundation". Ozone depletion, toxic wastes, acid rain, water scarcity and pol lution, forest destruction and topsoil loss are all part of this impending environmentall dis aster. Perhaps it is high time to consider underground nuclear testing as a part of this infa mous list. T Patterns of Earthquakes, M>=6, 1900 to 1988 For mcans of compwing patterns and trends of M>=6 earthquakes with nuclear testing, 1950 will be used as the watershed year. There were no nuclear tests in that year, and only nine covering the years 1945 through i 949. The idea is to identify patterns in the first half of this century (1900 to 1949) and compare these to the second half of the centu ry (1950 to 1988). The most evident trend from Table I is the change ill the comparative number of earth quakes of various magnitudes for the peri.od before and' after 1950. The first 50 years of tbis century recorded 3,419 such e..arthquakes of M>=6, an average of 68 per year. The last 39 years of this century recorded 4,963 earthquakes of M>=6, an average of 127 per year. In other words, the average per year for such earthquakes has about doubled in the second half of this century as compared to the first half of the century. Also, from 1900 NEXUS-"