Australian Dictionary of Biography

Keith Edward Bullen (1906-1976), seismologist and professor of applied mathematics, was born on 29 June 1906 at Auckland, New Zealand, eldest son of George Sherrar Bullen, a New Zealand-born linotype operator and later journalist, and his wife Maud Hannah, née Burfoot, from England. Keith was educated at Bayfield School, Auckland Grammar School (1919-22) and Auckland University College (B.A., N.Z., 1926; M.A., 1928; B.Sc., 1930). He taught at A.G.S. (1926-27) and lectured in mathematics at his former college (1928-31 and 1934-40).

In England in 1931 he entered St John's College, Cambridge (Sc.D., 1946), and soon decided to become a research student. Assigned to (Sir) Harold Jeffreys for supervision, he collaborated with him in constructing earthquake travel-time tables of greater accuracy than those that were then available. The work first appeared in 1935 and was republished in 1940 after its authors took into account the ellipticities of the different layers within the Earth. In 1932 Bullen had visited Europe and the Soviet Union (where he was arrested and tried as a spy for taking photographs in an unmarked military area, but was released). With permission to work away from Cambridge, next year he gave a special course of lectures at the University College of Hull. Back at Auckland, on 15 May 1935 he married Florence Mary Pressley at St David's Presbyterian Church.

Senior lecturer (from 1940) at the University of Melbourne, in 1946 Bullen accepted the chair of applied mathematics at the University of Sydney. He published An Introduction to the Theory of Seismology (Cambridge, 1947; 3rd edition 1963), Seismology (New York, 1954) and a text for first-year students, An Introduction to the Theory of Mechanics (1949; 8th edition 1971). In 1947 his and Jeffreys's findings had become the official tables of the International Association of Seismology and Physics of the Interior of the Earth. All Bullen's calculations were done on a manual Odhner desk-calculator: similar calculators were used in his department for research and teaching until electronic computers became available. Much of his later work was devoted to substantiating the theory of the Earth's solid inner core. Confirmatory evidence eventually came with the recording of free oscillations of the Earth following the earthquake in Chile in May 1960.

Bullen strongly supported the international scientific effort in seismology—the mathematical study of earthquakes and earthquake waves, and their paths through the Earth's interior. In his 1955 address as president (1954-57) of the International Association of Seismology, he proposed that the known times of nuclear explosions be published so that the resulting earthquake waves could be studied with greater precision. The idea was scientifically sound and seismic observatories now routinely record nuclear explosions. However, the proposal was then misunderstood by some and interpreted to suggest that nuclear bombs should be exploded at definite times for seismic purposes, which was certainly not his intention. Bullen was also vice-president of the International Council of Scientific Unions' committee on Antarctic research (1958) and of the International Union of Geodesy and Geophysics (1963-67), chairman (1971-75) of the international committee for the Standard Earth Model and a member (1973-76) of the governing council of the International Institute of Seismology and Earthquake Engineering, Tokyo.

His lectures showed his concern for the proper application of relevant mathematics to scientific problems, particularly in the Earth sciences; in addition, he stressed the need for clear exposition and good use of English. Bullen was always courteous, but his disagreement with T. G. Room, professor of pure mathematics at the University of Sydney, was widely known. The basis of their disagreement was Bullen's view that applied mathematics was a separate discipline to be studied for its own sake; Room held that pure and applied mathematics were inseparable, and should be taught together.

In 1968 Bullen was elected to the Pontifical Academy of Science, Rome. The iniative for his appointment came from his support for all seismological observatories, including those operated by the Jesuits. Despite his Anglican upbringing, he always preferred an agnostic point of view in his scientific work. Throughout his professional career he would not accept one theory over another until a crucial scientific test could be devised to settle the matter. When the geological controversy over continental drift arose, it was unfashionable to accept Alfred Wegener's theory; Bullen's view, that continental drift should not be rejected out of hand, was unpopular because one was expected to be either a 'drifter' or 'non-drifter'. His stand was vindicated as compelling evidence for the validity of continental drift became available, notably from rock magnetism.

Loaded with scientific honours in Australia and overseas, Bullen had been elected a fellow of the Royal Astronomical Society (1933), the Royal Society, London (1949), the Australian Academy of Science (1954) and the American Geophysical Union (1962). Among his many prizes and awards were the Bicentennial medal of Columbia University, New York (1955), the William Bowie medal of the American Geophysical Union (1961), the Day medal of the Geological Society of America (1963), the research medal of the Royal Society of Victoria (1966) and the gold medal of the Royal Astronomical Society (1974). He was an honorary fellow of the Geological Society of America (1963), the Geological Society of London (1967), the Royal societies of New Zealand (1963) and of New South Wales (1974), a foreign member of the American Academy of Arts and Sciences, Boston (1960), and a foreign associate of the National Academy of Sciences, Washington (1961). He was awarded honorary D.Sc. degrees by the universities of Auckland in 1963 and Sydney in 1975, and was guest lecturer at many universities and institutions at home and abroad. After he retired in 1971, he taught at the Seismological Institute in Tokyo and the University of British Columbia, Canada.

Bullen enjoyed travel and visited seismic observatories in out-of-the-way places to encourage the staff in their scientific work, and to ensure that they understood and appreciated the need for accuracy in interpreting seismic records, particularly in the timing of seismic onsets. He usually took the opportunity to add to his magnificent collection of coins. Physically, he was about 5 ft 6 ins (168 cm) tall and in his later years was conscious of his weight. Troubled by deafness from 1934, he managed quite well with a hearing-aid. He retired in 1971 and published The Earth's Density (London, 1975). Survived by his wife, son and daughter, he died of myocardial infarction on 23 September 1976 at Auckland and was cremated.