Frank Foster Evison, OBE, FRSNZ, Frank Evison was born in Christchurch in 1922. He graduated from Victoria University of Wellington with a BSc in physics in 1944 and an MA with Honours in mathematics in 1946. During this time he also served in the Royal New Zealand Air Force, where he gained a commission and became the commanding officer of a radar station. After the war, he traveled to Britain where he gained a Diploma from the Imperial College of Science & Technology and a PhD in geophysics from the University of London.
On his return to New Zealand, he joined the newly-formed Geophysics Division of the Department of Scientific and Industrial Research, where his early work was in exploration geophysics. He developed an electromagnetic transducer as a seismic source and then discovered coal-seam-guided S waves (Nature 176: 1224-5), which in 1985 Edwards et al. named 'Evison waves' (Geophysics 50:214-23).
The International Geophysical Year of 1957 included a major programme of exploration of Antarctica. Frank's contribution was a demonstration, using surface wave dispersion, that Antarctica was a continent with a crustal thickness of 30-40 km (Nature 83:306-8).
His research was becoming recognised and rewarded. He gained a Nuffield Fellowship in 1957 and a Fulbright Award in 1963.
In 1960 he became superintendent of the Seismological Observatory, a section of Geophysics Division, and in 1964 he became the Division's director. During this time he suggested an alternative explanation for observed palaeomagetic pole rotations, namely that they resulted from the slow flow of continental rocks under gravity (Nature 211:273-75). As a reason for poles' rotation it may have been wrong, but the idea that continental rocks could behave as fluids anticipated such thinking by decades.
Frank was an able administrator as well. During his directorship, the New Zealand seismograph network had a major upgrade. Many new stations were installed, including the first sets of three component seismographs at stations other than the Observatory's home in Wellington.
An example of Frank's direct approach to science is given by Evison's Wall. In the 1960s, there were many scientific questions about the then newly important Alpine fault, including whether, like parts of the San Andreas fault, it was creeping? Someone proposed that periodic surveys be conducted to test this. Repeated surveys would have been very expensive. Instead, Frank arranged to have a wall built across the fault at a location near Maruia. The wall still stands there, unbroken. The Alpine fault did not creep!
In 1967 he was appointed inaugural Professor of Geophysics at Victoria University of Wellington. Four years later he established the Institute of Geophysics. His vision was for an interdepartmental Institute with associate members outside the university as well. The Institute would thus provide a linkage for all those in Wellington who were active or interested in geophysics. So it remains today, notwithstanding many institutional changes over the years. The Institute of Geophysics continues to be an area of research strength at Victoria, and many graduate students who learned about the physics of the Earth at Victoria owe thanks to Frank for their education and their careers.
It was during the early 1970s that Frank began his research into earthquake forecasting that would continue until his death. His interest in earthquake occurrence was firmly rooted in his views about what science should be about and what a scientist's duty was. Earthquakes were a social threat that caused loss of life and suffering. It was therefore the job of science to do something to mitigate this threat. And it was Frank's self-imposed duty to do what he could, as a scientist, to enable that mitigation.
Frank was persuaded that the Earth signaled its preparation for large earthquakes. If one could read those signals, then warnings could be given and lives and property saved. The fact that prediction was difficult, that others tried and failed, and that yet other people were skeptical that it was possible at all, did not deter him. The easy problems could be left to others. An idea must be persisted with until it was proved to be wrong.
Frank's persistence with an idea led him into many heated arguments. His suggestion that earthquake faults may be 'but a gross form of earthquake damage' (Bull. Seism Soc. Am 53: 873-91) enraged his geologist colleagues. Later he admitted privately: “I was wrong, of course, but I had a lot of fun.”
His first interest in earthquake precursors was in the then newly proposed idea of dilatancy: that at a critical state of stress cracks would open in rocks, thereby altering their mechanical properties. Frank had acquired the first portable seismographs in New Zealand. In an early experiment, the focal mechanisms of aftershocks of the 1968 M 7.4 Inangahua earthquake, recorded in 1972, showed a major difference from the mechanism of the mainshock, which Frank and co-workers attributed to dilatancy (Nature 246: 471-3).
However, Frank's first attempt at a forecasting model was the precursory swarm hypothesis. Fluctuations in seismicity prior to a large earthquake could, Frank believed, be used quantitatively to forecast the subsequent event (Nature 266: 710-712). At about this time he started his collaboration on this work with a statistician, David Rhoades. The partnership continued until the day of his death.
Prediction of consequences from a theory is intrinsic in science. Therefore Frank argued that an earthquake forecaster's duty was to make predictions and test them against what would happen. He firmly believed that an assessment of reliability had to be part of any forecasting method. This required substantial testing, using data obtained subsequent to that from which the model had been constructed. He was so firm on this point that he successfully persuaded a New Zealand Prime Minister that a public announcement of a forecast was inappropriate because the method was inadequately tested. In discarding what he rightly called the anecdotal approach to earthquake prediction and insisting upon what is now known as prospective testing, Frank was decades ahead of the rest of the world.
In the late 1970s, scientific enthusiasm for earthquake prediction burgeoned. Frank helped to formulate an International Code of Practice for Earthquake Prediction. In 1979, he headed up a UNESCO conference on earthquake prediction in Paris, and was secretary and later chairman of the Commission on Earthquake Prediction of the International Association of Seismology and Physics of the Earth’s Interior.
In time, scientific enthusiasm waned. The view that earthquake prediction is impossible began to prevail. The arguments for this did not persuade Frank. As time went by and new data came to hand, the model for precursory seismicity evolved, reaching its culmination with the Precursory Scale Increase - or Ψ - phenomenon (Pure and Applied Geophysics 2004, 161:47-72) in which Frank and David provided 47 examples of an increase in seismicity prior to large earthquakes in California, Greece-Turkey, Japan and New Zealand.
In 1988 Frank retired from the chair of geophysics at Victoria. This meant that he had more time for research! Until a few days before his sudden illness and death he was not just a regular, but indeed a daily attendee at the Institute of Geophysics. He was often there at weekends and after hours. Prior to his retirement he made a full contribution to the academic life of the university through teaching, research and administration. He was an active member of the Professorial Board. After retirement his participation in the research activities of the university continued. He also continued to make a collegial contribution through social intercourse with staff and students, not only about science but also in debates about the events of the day, politics, music, and any of Frank's other interests that happened to be under discussion. As in his science, Frank often questioned the prevailing view of the issue, always for good reasons which he enjoyed arguing. If Frank approached you and said, "Now, you're a geophysicist…" or "You're a seismologist…" it was the preamble to a sharp question that would require you to agree with him or argue convincingly against a new idea. Most of this activity took place in the School of Earth Sciences, but Frank did not forget his roots as a physicist, and continued to give seminars to his colleagues in the School of Chemical and Physical Sciences.