By Emeritus Professor Paul Davis, with contributions from Emeritus Professor Peter Bird
Professor David Jackson passed away on 30 March 2023 at his home in Pacific Palisades, California. He is survived by his wife Kathy and children Kelly and Morgan. As a person Professor Jackson was a kind man with a wonderful sense of humor, and was ever ready to lend a helping hand to some whom others might pass by.
Professor Jackson graduated in Physics at Caltech in 1965, followed by a PhD in geophysics at MIT in 1969. He was appointed Professor in Residence/Researcher at UCLA in 1969, then Assistant Professor in 1972, and he retired as a Distinguished Professor in 2011. He was Chair of the Department 2004-2008 and held a joint appointment in the Institute of the Environment and Sustainability, 2008-2011. He served as Director of the Southern California Earthquake Center, 1996-1999. His expertise was sought after by numerous government and professional bodies.
He, along with Yan Kagan, led what is regarded as the foremost earthquake-statistics team, guided by a principle espoused in the title of his early article ‘Interpretation of Inaccurate, Insufficient, and Inconsistent Data.’ His first demonstration of this philosophy was his deflation of the Palmdale bulge. In the mid-seventies repeated surveying suggested a large bulge in the ground had developed around the section of the San Andreas fault near Palmdale, California, similar to bulges that had been reported before giant Chinese earthquakes. There was considerable worry that Los Angeles was about to experience a huge earthquake. He applied his analysis to reveal that the data supporting the bulge could be explained by cumulative, hitherto-hidden, surveying errors. A controversy ensued, but the earthquake never happened, and few now think a bulge ever existed.
Professor Jackson’s research then progressed to set up the formalism to put earthquake prediction into a statistical framework. Earthquake prediction has been a subject rife with anecdotal evidence, optimistic interpretation, and reinterpretation of pre-earthquake events. This set the stage for the statistical likelihood testing methods that were used by Professor Jackson and continue to be used by colleagues today. He encouraged the use of the word ‘forecasting’ rather than ‘prediction’ to reflect the uncertainties involved. In many of his later papers his ideas on forecasting are central to their subject matter. In particular, his quantification of the clustering model in which a forecast is based on the proximity in space and time of recent earthquakes appears to hold more promise than the accepted paradigm in which earthquakes occur in relatively quiet ‘gaps’ along plate boundaries.
He issued a challenge to earthquake forecasters to make prospective rather than retrospective forecasts. Largely as a result of his input, SCEC (Southern California Earthquake Center) set up an earthquake forecasting contest called RELM (Regional Earthquake Likelihood Models) in which different ideas are translated into earthquake probability as a function of space, magnitude, and time, against which null hypotheses can be compared in a formal manner. Different groups across the country, including Prof. Jackson’s, signed up for RELM and contributed a 5-year forecast. After the 5-years had elapsed, the results were published by the National Academy of Sciences. The HJK forecast, authored by Agnes Helmstetter, Jackson and Kagan, based on his clustering model, is still (Bayona et al., 2022) regarded as one of, if not the most successful method.
Professor Jackson became an important consultant for translating current earthquake forecasting knowledge into policy documents. He served on the National Earthquake Prediction Council which wrote the blueprint for prediction-evaluation procedures. He also served on the Science Review Committee engaged in writing the report of the Working Group on California Earthquake Probabilities, a report that was used in the National Seismic Hazards Mapping Program, and in setting earthquake insurance rates in California. Without his input, earthquake insurance rates at that time would have been much higher.
As his career progressed his interests extended from earthquakes to environmental issues. Under Professor Jackson’s leadership as Chair, he established an effective dialogue between the units and departments involved in Geoscience research at UCLA (Departments of Earth and Space Sciences, Atmospheric and Oceanic Sciences, and the Institute of Geophysics and Planetary Physics, among others) to launch the Geosciences Initiative. He recognized the limitations of Departmental boundaries, many of which were drawn nearly a century ago. The geosciences served as an archetype example of complex system science with relevance to climate, environment, natural hazards and energy, the understanding of which requires pooling expertise across traditional boundaries. As a result of his efforts new FTE were added, and inter-departmental linkages now flourish.
His teaching also reflected this widening interest, and included Environmental Geology of LA, a course he designed, as well as the graduate course on Inverse Theory, one on Earthquakes, a Fiat Lux on Oil and Water, and a new offering Environmental Science, a course for the interdepartmental major of the same name. Students described his classroom approach as supportive and were stimulated by his ‘passion’ for the subject. Special note was made of his environmental field trips.
He has organized special sessions at the Fall meetings of the American Geophysical Union, including one on energy resources, as the price of gas soared, and one on the Effectiveness of Natural Disaster Scenarios, furthering his understanding of the environment and its extremes.
He served on the panel that designed the interdepartmental major in Environmental Science and was instrumental in getting that program established. It now has over 450 majors. As a result of these initiatives, he was invited to hold a joint appointment in the Institute of the Environment and Sustainability.
Professor Jackson served as Secretary of the U.S. National Committee of the International Union of Geodesy and Geophysics (IUGG), and on its Finance committee and set up a program for the IUGG General Assembly. He wrote the document used by member nations to request support from their governments. The U.S. National Committee selected him for the US representative on the Governing Bureau of IUGG.
In his 54 years since arriving at UCLA in 1969, Professor Jackson rose to a position of national and international distinction that implicitly recognized the need for his careful statistical approach in assessing the likelihood of natural hazards such as earthquakes, as well as his preeminence in this area. His nomination to leadership positions in the foremost world organization in geophysics (IUGG), his contributions to the State of California’s earthquake preparedness and insurance issues, to the University in the Geosciences and Environmental Sciences initiatives, and his contributions to the morale of staff, students and faculty in the Department leave us a legacy of intellectual rigor, dedicated energy, and human warmth which will be a model for the next generation.