A Tribute for Nicholas N. Ambraseys, Honorary Member, by Edmund Booth

Prof. N. N. Ambraseys

Nicholas Neocles Ambraseys (1929-2012) was one of the towering figures of engineering seismology, who played a key role in the development of the discipline for more than half a century - from before the foundation of the IAEE in 1963 (he attended the committee meetings in 1960 that led to its establishment) right up to the time of his death at his London home on 28^th December. He was born to Greek parents and educated in Athens, although his mother was born in Alexandria and most of his professional life was based in the United Kingdom; he also spent extended periods abroad on earthquake field missions all over the world and had many strong academic links to continental Europe, the United States and elsewhere. His therefore was a truly international career; he used his ease in diverse cultures and languages in a very distinctive way to make important contributions to many aspects of our discipline. Most notable of these contributions were advancing the understanding of seismic slope stability, his collection and rigorous interpretation of earthquake field data, his pioneering use of historical documents for establishing extended records of seismic activity and (equally importantly) his inspirational teaching and mentoring of many generations of seismic engineers. He developed many tools to help the world cope better with earthquakes, and that contribution will be lasting.

Brief curriculum vitae

Nick Ambraseys studied engineering at the National Technical University of Athens, graduating in 1952. After a period on the staff of NTUA in the Department of Fluid Mechanics, he went on to Imperial College London, where in 1958 he obtained his PhD under Alec Skempton and Alan Bishop; his subject was "The seismic stability of earth dams". That year, he joined the staff of Imperial College, where ten years later he established the Engineering Seismology Section, and was appointed full professor of Engineering Seismology in 1974. In 1994, at the age of 65, he "retired" with the title Emeritus Professor, but maintained the post of Senior Research Investigator; retirement made little difference to his professional output or his presence in the College, and indeed one third of his papers and three of his six books were published after retirement. He received many honours during his lifetime, including in Britain election to the Royal Academy of Engineering and life membership of the Society for Earthquake and Civil Engineering Dynamics, in Greece membership to the Academy of Athens (one of only two engineers on this small, prestigious body) and in the USA honorary membership of the Earthquake Engineering Research Institute. In 1986 he was elected an honorary member of the European Association of Earthquake Engineering, of which he was a founder member, prime instigator and sometime secretary and vice president and he was also an honorary member of the International Association, on which he served as UK representative for a time. Fuller details of his career, and an affectionate tribute to his qualities by those who knew him well, can be found on
http://cires.colorado.edu/~bilham/Ambraseys.html .

Appreciation

A seminal early event in Nick's career occurred in 1956. In that year, an earthquake of about M=7.5 centred under the Mediterranean Sea caused much damage and triggered the largest 20^th Century tsunami in the eastern Aegean. His study of the effects of the earthquake and tsunami on harbours in the Greek archipelago brought together a number of the interests which were to dominate the rest of his professional career - seismic slope stability, field studies of earthquakes and the use and interpretation of historical documents; this third interest featured in a paper¹ he published in 1960 on the tsunami.

Seismic slope stability was an early interest, including the deformation and displacement of slopes, soil liquefaction and other geotechnical aspects of earthquake engineering. The subject of Nick's PhD thesis, this work was continued by Sarada Sarma, the first PhD student to graduate in 1968 from Nick's newly established department of engineering seismology at Imperial. Previously, Nick had worked for a time with another giant of earthquake engineering, Nathan Newmark; in his famous 1965 paper² on the sliding block method for estimating soil displacements in earthquakes, Newmark acknowledged Nick for his comments and suggestions. The interest extended to geotechnical design consultancy, and Nick provided advice on the design and siting of some twenty large dams in seismic environments.

Papers on field studies of earthquakes, the second of his major interests, form two thirds of his output and between 1963 and 1981 Nick undertook around 30 field missions all over the world, usually as leader of a UNESCO mission. Missions for Nick were not for some vague or touristic purpose; he used them to collect quantitative data from the seismological effects of earthquakes, which were later used to produce relationships for rupture length, surface slip, earthquake magnitude and macroseismic intensity. He was still publishing from the data in his field notebooks into his eighties. Nick wrote in his Mallet-Milne lecture of 1988³ "···.the site of a damaging earthquake is undoubtedly a full-scale laboratory, in which significant discoveries may be made by keen observers - seismologists, geologists, engineers, sociologists and economists, not to mention politicians." He added "I feel that any advancement of our knowledge about the assessment and mitigation of earthquake risk should be accompanied by a growth in our accumulation of reliable observational data···.. much computer effort has been diverted to solving problems based on guessed parameters and more data from field observations are now required." He warned sternly "There is little room in Engineering Seismology for 'armchair' seismologists and engineers".

These two areas on their own would have been more than sufficient for most careers, but some of Nick's most important and lasting contributions to engineering seismology were in yet a third - the study of historical accounts of earthquakes. It is easy to see that an instrumental catalogue going back only a hundred years is insufficient for establishing the very low probability event required for a nuclear power station, particularly in seismically quiet regions like the United Kingdom. Nick's work showed they can also mislead in highly active areas like Anatolia, where his use of historical records clearly demonstrated fluctuations in activity levels with a timescale of many hundreds of years, directly contradicting the usual assumption of stationarity. The implications for estimating seismic hazard are immense. Nick's ability in language, his experience of different cultures and his interests in fields outside engineering as well as his rigorous examination of sources made him perhaps uniquely suited to the subject. His collaboration with the historian Charles Melville resulted in the 1982 publication of the seminal work 'A history of Persian earthquakes⁴, which demonstrated all these qualities, and later collaborations, including that with Robin Adams, produced a series of books which continued to exploit these methods. His sixth and final book,⁵ a magisterial study of the seismicity of the eastern Mediterranean and Middle East, was published in 2009, when he was eighty.

Nick's multi-faceted career covered other aspects too, notably the study of strong motion data. He started the systematic collection and cataloguing of strong motion records in 1971, and was centrally involved in the establishment of the Internet Site for European Strong-motion Data, which had its roots in these earlier efforts of Nick. He also published predictive equations for earthquake-induced ground displacements and the maximum distance at which liquefaction may occur, equations that are still in use today.

Future generations can only progress by standing on the shoulders of the giants who went before them, and there is no doubt that in our field, Nick was one of those giants. His work left its mark on numerous students in the many fields in which he was active, and he is widely acknowledged as an inspirational teacher and mentor. He left the world much better prepared for earthquakes than he found it, and his legacy will surely endure.

This tribute was prepared by Edmund Booth, with much help from friends and colleagues at Imperial College, and elsewhere.