ROBERT STONELEY

14 May 1894 — 2 February 1976

Elected F.R.S. 1935

By S ir H arold Jeffreys, F.R.S.

Robert Stoneley was born at 102 Mayola Road, Clapton, London E.5, on 14 May 1894. His father, also Robert, was a builder, and his mother was Fanny, nee Bradley. He had one younger brother, Maurice. The house was close to where the railway crosses the River Lea. He married (28 March 1927) Dorothy Minn, whom he had known since childhood; her parents were Gayford Duge Minn and Annie, nee Okey, sister of Thomas Okey, sometime Professor of Italian at Cambridge. There are two sons, Robert and Anthony John Martin, born 1929 and 1944; a daughter, Ruth Margaret, who was born in 1931 died in 1940. Both sons are members of Pembroke College and Ph.D.’s of the University of Cambridge. Robert is a geologist with the British Petroleum Company, and Anthony a computer officer at the Cambridge University Com­puter Laboratory.

Stoneley was at Parmiter’s School 1904-10, then at the City of London School, 1910-12, where he got the Mortimer Exhibition for Science and medals for arithmetic and chemistry and also a Leaving Exhibition awarded by the Worshipful Company of Broderers in 1912.

He entered St John’s College, Cambridge, in 1912 with a ,£40 Foundation Scholarship in Natural Sciences. Pie obtained first classes in Part I of the Mathematical Tripos in 1913, Natural Sciences Part I in 1914 and Mathematics Part II with distinction in Schedule B in 1916. He took his B.A. in 1915 and M.A. in 1920, and was awarded the Taylor Research Studentship in 1916.

He was in the Army (Non-combatant Corps) 1916-20, having applied for the R.A.M.C. His demobilization was apparently delayed because nobody was in a position to offer him a definite post. He returned to St John’s in 1920 and proceeded to research in geophysics. He soon went to Sheffield as a temporary lecturer and later assistant lecturer in mathematics until in 1923 he went to Leeds as assistant lecturer and later lecturer under Professors W. P. Milne and S. Brodetsky; in 1933 he was made Honorary Reader in Geophysics. At Leeds he was Honorary Astronomical Observer; there was a large reflector attached to a sidereal clock on Woodhouse Moor at the time. Brodetsky was

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President of the Leeds Astronomical Society also at this time and Ernest Tillotson, who was Secretary, remembers spending many hours with Stoneley at the telescope. I recollect his being called on to give evidence in a police court case about poaching, when he had to determine the hour of legal twilight. He was also a member of the Leeds Geological Association and joined in all the field excursions of the University Geology Department.

He returned to Cambridge in 1934 as a University Lecturer in Mathematics. He was a Supervisor in Mathematics at Emmanuel College 1935-46 and Director of Studies and College Lecturer at Pembroke College 1936-61; he became a Fellow of Pembroke in 1943 and Stokes Lecturer in the University in 1949. He was Reader in Theoretical Geophysics from 1949 to 1961, when he retired. Until 1949 he lectured regularly on statistics and dynamics for Parts I and II of the Mathematical Tripos. During the war of 1939-45 he remained in Cambridge and had a very heavy teaching programme as well as serving as a Senior Air Raid Warden and in the Home Guard. Throughout his career he lectured at various times on waves and tides, boundary layer theory in viscous motion, dynamical meteorology and elastic vibrations with reference to seismology.

From 1961 to 1963 he was Seismologist at the U.S. Coast and Geodetic Survey, Office of Research and Development, Washington, D.C., and from 1963 to 1967 he was Professor of Geophysics at Pittsburgh University. He greatly enjoyed this work during his ‘retirement* and the friendship of his American colleagues. He had previously been a Visiting Professor at the Uni­versity of California (1948) and at the American University, Washington, D.C. (1955-56), where he was also a guest worker at the National Bureau of Stan­dards; he was an Honorary Research Fellow in Geophysics at the California Institute of Technology in the summer of 1956.

He took his Sc.D. in 1931 and became a Fellow of the Royal Society in 1935. His Fellowship of the Royal Astronomical Society dates from 1921; he was Secretary of the Geophysical Committee from 1932 to 1945. This involved editing the Geophysical Supplement and arranging about five discussions per year. (I never understood how he managed to arrange the Geophysical Discus­sions in advance for a whole year. When I had the job, people asked to take part always said either that the notice was too long or too short.) He was Chair­man of the British Association Seismological Committee from 1946 to 1975. From 1957 to 1963 he was Director of the International Seismological Summary. From 1934 onwards he served on the National Committee for Geodesy and Geophysics and its subcommittees. He was on the Council of the Royal Society from 1951 to 1953 and represented the Society on the National Committee for Astronomy from 1940 to 1945. He was President of Section A/A* of the British Association for 1960-61 and gave his address on ‘The interior of the Earth’ at the Norwich meeting. This was the key paper on which a morning of lectures on seismology was based.

He took an active part in the International Union of Geodesy and Geo­physics, in particular of the International Seismological Association, of which

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he was Vice-President in 1944 and President from 1945 to 1951. At the meet­ings in 1948 and 1951 of the I.U.G.G. he was the U.K. national representative. He was on the British National Committee for the International Geophysical Year. In 1962 he was appointed by Unesco as one of three Senior Consultants during the development of the Institute of Seismology and Earthquake Engi­neering, Tokyo. He was a Fellow of the American Geophysical Union and was elected to the Pontifical Academy of Sciences, Vatican City, in 1970 and was made an Honorary Member of the Seismological Society of America in 1973.

Stoneley remembered that from the age of 12 he had a great passion for chemistry, and it was mainly on chemistry that he was awarded his college scholarship. On entering Cambridge he had every intention of specializing in chemistry, but on the advice of his tutor (R. P. Gregory) he spent his first year on Mathematics part I. He was much impressed by the teaching of Dr H. F. Baker, Dr T. J. I ’A. Bromwich and Mr E. Cunningham. In his second year he found that his interest in chemistry was waning somewhat, and in his third and fourth years he returned to mathematics. At that time St John’s was the only college that had lecturers covering the whole of Part I and Schedule A. Even Trinity men came to Baker’s Theory of Functions.

One of his first papers (2) concerned elastic waves where two solids are welded together at a plane. It was known that for one solid with a free surface a type of progressive (Rayleigh) wave was possible, such that the motion died down exponentially with distance from the boundary. Stoneley showed that this could also happen with a double solid, the motion in both solids dying down with distance from the boundary. This appeared to be only a mathe­matical curiosity, but waves of this type have now been detected and are known as Stoneley waves. Incidentally this paper was the first to make use of the notations a and ft for the velocities of longitudinal (P) and transverse (S) waves.

He pointed out a major mistake in the interpretation of the surface waves of earthquakes (3). Gutenberg had studied their periods and velocities, and assumed that the velocity associated with a given period was the wave velocity. Stoneley showed that it was the group velocity, and the result was a great reduc­tion in the inferred thickness of the Earth’s upper layer.

There had been (and indeed still are) remarkable failures of communication among writers on the structure of the Earth. R. D. Oldham in 1906 showed that the Earth has a central region where the velocity of P is substantially less than in the outer part. E. Wiechert (1897), in trying to reconcile the Earth’s ellipticity with a theory ascribing it to hydrostatic deformation due to rotation, inferred that the radius of the core was about 0.78 of the outer radius. He used a shell and core of uniform densities. Gutenberg (1914), starting with Oldham’s data, inferred from travel times that the drop in the velocity of P was at about 0.55 of the outer radius. Revised travel times had been given by K. Zoppritz (1907) and extrapolated to the anticentre by H. H. Turner, taking no account of any discontinuity. In 1915, with rough estimates of the density and elastic properties based on Wiechert’s model, I estimated the period of the free

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(Eulerian) nutation, which is affected by elasticity, and found it too short. In 1919 C. G. Knott derived velocities from the Zoppritz-Turner times (this had already been done for better times by S. Mohorovicic) and in 1926 Stoneley calculated the free period using these velocities. The arithmetic was very heavy and was done on an ancient Brunsviga lent by Udny Yule. The period again came out too short, but I noticed that the densities used made no correction for the compression of matter due to the overlying matter, and therefore, while retaining uniform densities, took these and the radius of the core all as unknown and redetermined them to fit the free period. The result was that the radius of the core had to agree very closely with that found by Gutenberg and that the core had to have a negligible rigidity. I remember sending a postcard to Stone- ley: ‘Die Wiechertsche und Oldham—Gutenberg Kerne identisch sind.

I showed incidentally that the differences between my revised densities and Wiechert’s were a natural consequence of compression, which of course Wiechert had no means of evaluating.

Gutenberg had thought of the possibility of a liquid core but rejected it, though he had found waves of P type in it but none of S type. He thought that S waves might enter the core but be rapidly absorbed. Stoneley s calculation gave the first clear evidence that in a large part of the Earth the rigidities implied by the Zoppritz-Turner times were much too high. This work goes back to Kelvin’s proof, from the amplitudes of tides, that if the Earth was uniform its rigidity would be about that of steel. Seismology had shown that the average rigidity down to the core was much greater than that of steel and agreement with the facts could be attained only if that of the core was very small.

He did several papers on surface waves, including one with E. Tillotson on the effect of a double surface layer on Love waves; the results are complicated and their interpretation remains difficult. The calculation has now been done for many models more rapidly by electronic computers.

The work on deep-focus earthquakes (12) was a major contribution. Turner, in his work for the International Seismological Summary, used the interval between P and S from the Zoppritz-Turner times as a means of estimating the distance of the epicentre of an earthquake from the station. For most earth­quakes, arcs about the stations met closely near a point, which was taken as the epicentre. But sometimes the arcs failed to meet, sometimes they overlapped considerably. Turner interpreted this as being due to the earthquakes being at a considerable depth, sometimes some hundreds of kilometres, and in some cases as being well above the average level. (At large distances focal depth reduces the actual distance and hence the times of travel.) His results in some cases were confirmed by K. Wadati. It was known by that time, largely owing to the work of A. Mohorovicic and Gutenberg, and indeed by a study by Turner himself, that the Zoppritz-Turner times had errors of up to 30 s, which is of the order of Turner’s differences. It also seemed possible that Wadati’s results might be due to misidentifications, some upper layer phases being identified as the usual P and S.

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Barrell’s work on imperfection of isostasy had indicated that the Earth has a considerable strength to these depths, and consequently I welcomed Turner’s result, but wanted further confirmation. I pointed out to Turner that a crucial test could be derived from a well known reciprocity theorem in dynamics. An impulse at a node of a free vibration cannot excite that vibration. For surface waves the whole of the Earth below something of the order of a wave length effectively consists of nodes. Consequently a deep-focus earthquake should excite very small surface waves or none. This could be tested by a simple inspection of the seismograms. But Turner was so satisfied by his own argu­ments that he would not look. (This phenomenon had occurred earlier in geo­physics and continues to the present time.) Stoneley, however, after Turner’s death, examined many of the Oxford records, and did find small or no surface waves in the alleged deep earthquakes. ‘Long waves’, which in a normal shock are surface waves, were often reported in the I.S.S., but Stoneley noticed that these did not occur at the normal times for surface waves, but at the times of various reflexions at the surface, which would occur for any depth.

At about the same time F. J. Scrase found reflexions in deep shocks at short distances analogous to the rays that form the image in a concave mirror. Stoneley’s and Scrase’s methods were free from the effects of errors in the travel times and of misidentifications. The existence of deep foci was therefore established. Further work on them has led to great advances.

This work did not explain what Turner called ‘high focus’. Byerly’s readings of the Montana earthquake (1926) showed phases at near stations at about the times for upper layer phases in Europe, but his times at great distances agreed reasonably with those Turner had got (1926) in a rediscussion of I.S.S. data. It therefore appeared that the focus of the Montana earthquake was shallow and so were those of Turner’s average earthquakes. The need for an explanation of ‘high focus’ remained. However J. S. Hughes noted that an earthquake in Mongolia of 1931 August 10 would have been interpreted as of high focus, on account of the large interval between P and S. Stoneley (20, 22) studied the residuals in detail and noted, both for P and S, separate maxima of frequency. If the earliest of each was taken the intervals would be about normal. The suggestion was that actually there were two earthquakes (or even three) some seconds apart, the later one being the stronger. Foreshocks and aftershocks were of course known phenomena. The observer could read the first move­ment as P, but S enters on a disturbed background, and if he is looking for a large movement after P he would be likely to read the second S. Tillotson (1938) examined many cases where high focus had been inferred and found evidence for this sort of multiplicity.

The result was of great importance, since it implied that there might be many cases* where an observer had read the first P and a later S, and if simple means were taken the travel times of S would be overestimated. Consequently, in my later work I concentrated on earthquakes where over considerable ranges of distance the S residuals looked consistent, indicating that the observers had read the same thing. I have not noticed any recent comment on multiplicity,

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and suspect that this precaution has been neglected. Multiplicity seems much rarer in deep shocks than in shallow ones.

It was noticed, particularly by J. B. Macelwane, that what appear to be Rayleigh waves sometimes have a transverse component. Stoneley (17) showed that when the properties change along the path refraction becomes complicated. The change of direction of a wave front is dependent on the wave velocities, the time of travel of a given period on the group velocities. A continental coast inclined to the direction of travel could produce the effect.

He wrote, either alone or in collaboration, many papers on surface waves and some on microseisms and tsunamis (sea waves produced by earthquakes). It was known theoretically that when there is a maximum group velocity there is little motion before a wave with this velocity would arrive, and that the first motion would be the largest and would be followed by a train of decreasing amplitude. Stoneley showed that this corresponded with observation. He also studied the propagation of waves in anisotropic media.

He also wrote some valuable historical articles (29, 44) on the history of the International Seismological Summary. This was started by John Milne and continued by H. H. Turner as the British Association Seismological Bulletin. It became the I.S.S. in 1922. It collected observations from all over the world and calculated epicentres and (later) depths of focus. Finance has always been a major problem; cost was shared between the Bureau International de Seismo- logie of Strasbourg and a grant from Oxford University. The work was done at Oxford by Turner himself, J. S. Hughes and Miss E. F. Bellamy. After Turner’s death Hughes and Miss Bellamy continued the work; when Hughes was on war service Miss Bellamy continued alone. I became Honorary Director in 1947; Stoneley succeeded in 1957, Dr P. L. Willmore in 1963 and Dr E. P. Arnold in 1970. Expense grew greatly with increase of data and of the cost of living. The British Association, Unesco and H.M. Treasury made contributions; Unesco’s policy, however, was to encourage new projects and not the continuation of permanent services, and its grants kept decreasing. Fortunately the International Union of Geodesy and Geophysics, through the Federation of Astronomical and Geophysical Services, and several countries, led by Canada, came to the rescue.

The B.A. Seismological Subcommittee is reappointed annually. It reports on the progress of seismology in this country, and administers the Gray-Milne Fund, started by John Milne, and the Crombie Bequest. The Gray-Milne Fund is strictly to support research; in addition the Caird Fund of the B.A. and the Crombie Bequest have been used occasionally to pay for part of the printing of the I.S.S. During the time when Stoneley was Director financial shortages became so serious that it was necessary to omit the ‘additional read­ings’. Most observatories reported on P and S, but a fair number reported other phases, especially the near reflexions pP and sS and the core phase These were of the greatest value in estimating focal depths and in studying properties of the core, and the loss was serious. Part of this information is now given again by the International Seismological Centre, and during Arnold’s

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study of Japanese deep foci many readings were recovered by Professor J. P. Rothe from the station bulletins. The value of the many years that Stoneley devoted to the work of the B.A. Seismological Committee and to the I.S .S . cannot be overestimated. He preserved a file of correspondence relating to the years 1939 to 1950, and this is now in the keeping of the International Centre.

I was two years senior to Stoneley at St John’s and knew him as an under­graduate. He and E. P. Farrow, a plant ecologist who introduced me to Karl Pearson’s Grammar of science, taught me to ride a bicycle and we have both maintained our interest in cycling and botany throughout our lives. Our first tour together (1915) was in the Isle of Wight and the New Forest. At that time (and a long time after) the International Seismological Summary (then the British Association Seismological Bulletin) was printed at Shide, near Newport, I.o.W., by the Isle of Wight County Press, and we visited the Observatory there. This was founded by John Milne, who had designed the old Milne seismo­graph, essentially a bar free to swing about a nearly vertical support. It was not a satisfactory instrument, on account of small magnification and insufficient damping, but J. J. Shaw greatly improved it. Mr Burgess, of the Press, had also improved it in a different way. As it happened, Professor H. H. Turner, J. J. Shaw and Burgess were at the Observatory at the time and showed us the instruments. John Milne had died; Mrs Milne (a Japanese) was still living at Shide, but we did not meet her. We later did many cycling tours together, to Devon, Wales, the Wye Valley, the Lake District, Yorkshire and Teesdale. After his marriage and return to Cambridge I was a frequent visitor at his home and had much kindness from him and his wife. He always enjoyed wel­coming students to his home. We also attended many British Association meetings and conferences abroad together. His unassuming and friendly manner, coupled with his keen interest in his subject and his readiness to help others with their work, made him many friends here and abroad, particu­larly in the United States and Japan. We were at a conference at Stuttgart once, where in post-war reconstruction the Germans had scraped together all the rubble from demolished buildings and piled it outside the town as a memorial. He deprecated this, saying that it should have been used in making foundations for new buildings. Presumably his father’s business inspired this remark.

He was also interested in music and was a good amateur pianist as an undergraduate.

In the winter of 1974-75 he had two operations, but he made a good recovery and a party was arranged at Emmanuel College for his eighty-first birthday and many friends were present.

I am grateful to Dorothy Stoneley and to Mr Ernest Tillotson for help in the preparation of this memoir.

The photograph is by Walter Bird.

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The effect of the ocean on Rayleigh waves. Mon. Not. R. Astr. Soc. Geophys. Suppl. 1, 349.

The elastic yielding of the Earth. Mon. Not. R. Astr. Soc. Geophys. Suppl. 1, 356.

(With E. T illotson) The effect of a double surface layer on Love waves.Mon. Not. R. Astr. Soc. Geophys. Suppl. 1, 521.

A Rayleigh wave problem. Proc. Leeds Phil. Soc. 1, 217.The dispersion of waves in a double superficial layer. Mon. Not. R. Astr.

Soc. Geophys. Suppl. 1, 527.Love waves of short wave-length. Proc. Leeds Phil. Soc. 1, 459.The effect of variation of density on the propagation of surface waves on

an elastic solid. Proc. Leeds Phil. Soc. 2, 103.Some near earthquakes reported in the International Seismological Sum­

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Geophys. Suppl. 2, 429.On the crustal warping hypothesis. Mon. Not. R. Astr. Soc. Geophys.

Suppl. 3, 176.The transmission of Rayleigh waves in a heterogeneous medium. Mon.

Not. R. Astr. Soc. Geophys. Suppl. 3, 222.On the apparent velocities of earthquake waves over the surface of the

Earth. Mon. Not. R. Astr. Soc. Geophys. Suppl. 3, 262.The refraction of a wave-group. Proc. Camb. Phil. Soc. 31, 360. Surface-waves associated with the 20° discontinuity. Mon. Not. R. Astr.

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4, 562.Times of travel of the L-phase. Seismology Symposium, British Associa­

tion, Cambridge (1938). Trans., p. 17.The interior of the Earth. Occasional Notes of the R. Astr. Soc., no. 8, 103. The continental layers of Europe. Bull. Seism. Soc. Amer. 38, 263.The seismological implications of aeolotropy in continental structure.

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Microseisms of high frequency. Pontificiae Academiae Scientiarum Scripta Varia 12, 151.

The communication of energy of ocean waves to the ocean floor. Pontificiae Academiae Scientiarum Scripta Varia 12, 389.

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The propagation of surface elastic waves in a cubic crystal. Proc. R. Soc. Bond. A 232, 447.

The thickness of the continents. Vistas in Astronomy 2, 842.Lectures—Surface waves in elastic media. Nat. Bur. Stand. Wash., D.C.,

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Verh. geol.-mijnb. Genoot Ned. ( GeologSer.) 18, xxxv. (With U. H ochstrasser) The attenuation of Rayleigh waves with depth

in a medium with two surface layers. Mon. Not. R. Astr. Soc. Geophys. Suppl. 7, 279.

The variation of amplitude and energy with depth in Love waves. Contri­butions in Geophysics: in honor of Beno Gutenberg (ed. H. Benioff et al.), p. 36. London: Pergamon Press.

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The International Geophysical Year. Nature, Bond. 188, 529.Obituary notice of Professor Beno Gutenberg. Nature, Bond. 188, 433. Obituary notice of A. W. Lee. Comptes Rendus no. 13, I.A.S.P.E.I., p. 49. The propagation of surface waves in anisotropic media. Partial differential

equations and continuum mechanics (ed. R. E. Langer), pp. 81-93. Madison: University of Wisconsin Press.

The distribution of seismic stations. Seismological Symposium, 5th C.S.A.G.I. Assembly, Moscow, 1958. Annals 11, 367.

The oscillations of the Earth. Phys. and Chem. of Earth 4, 239.Sir Harold Jeffreys. An appreciation. Geophys. J. R. Astr. Soc. 4, ix. (With U. H ochstrasser) The transmission of Rayleigh waves across an

ocean floor with two surface layers. II. Numerical. Geophys. J. R. Astr. Soc. 4, 197.

Present-day tendencies in seismology. I.C.S.U. Rev. 3, 66.The development of the International Seismological Summary. Proc.

I.S.S. Committee, Paris, July.The interior of the Earth (Presidential address, Section A, British Associa­

tion). Advanc. Sci. 18, 339. Also summary in Nature, Bond. 191, 983. The Halley Bay expedition of the Royal Society. Nature, Bond. 192, 1004. The study of tsunamis. U.S.C. and G.S. Res. and Devt Annual Scientific

Report.The propagation of tsunamis. Geophys. jf. R. Astr. Soc. 8, 64.

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1963 The propagation of surface waves in an elastic medium with orthorhombicsymmetry. Geophys. J. R. Astr. Soc. 8, 176.

The scouring effect of tsunamis. Proceedings, Seismology data analysis center dedication, April, p. 37.

Review: Rutherford at Manchester, Birks, J. B. (ed.). Trans. Am. Geophys. Un., 44, 1023.

1964 Modern trends in seismology (Review of K. E. Bullen’s Seismology, 3rded.). Nature, Lond. 202, 632.

1965 The polarization of distortional waves in an isotropic medium. Geophys.J. R. Astr. Soc. 9, 219.

1965 Microseisms in the western Atlantic region. Annals of the I.G .Y. 30, 67. Oxford: Pergamon Press.

Microseisms in the eastern Atlantic region. Annals of the I.G .Y 30, 69. Oxford: Pergamon Press.

1967 Tsunamis—or seismic sea waves. International Dictionary of Geophysics 2, 1598. Oxford: Pergamon Press.

International Seismological Summary. International Dictionary of Geo­physics 1, 757. Oxford: Pergamon Press.

History of modern seismology. International Dictionary of Geophysics 1, 724. Oxford: Pergamon Press.

Surface waves in elastic media. International Dictionary of Geophysics 2, 1492. Oxford: Pergamon Press.

1967 Love-waves of high frequency along an interface. Geophys. J. R. Astr. Soc.13, 161.

Joseph Steel Hughes (obituary). Quart. J. R. Astr. Soc. 8, 293.Regional variations in Earth tides: paper read at the International Associa­

tion of Geodesy.City living on a fault. Geogrl Mag., Lond. 40, June, 122.

1968 Policy for earthquakes. Geogrl Mag., Lond. 41, October, 73.1969 Geophysics. In: Scientific thought, 1900-1960, pp. 106-122. Oxford:

Clarendon Press.Hugo Benioff (Obituary). Quart. J. R. Astr. Soc. 10, 164.

1970 The history of the International Seismological Summary. Geophys. J. R.Astr. Soc. 20, 343.

An eyewitness account of the Great Earthquake of San Francisco, 1906 (A review of ‘To go among strangers’, by Dorothy A. Buchanan, A. H. Stockwell, 1969). Geogrl Mag., Lond. 42, May, 619.

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