David Sandwell is the preeminent leader in applying satellite altimetry data to determine the marine gravity field and seafloor topography to elucidate the thermal and mechanical behavior of the oceanic lithosphere. Through his deep knowledge of space-based radar mapping and altimetry he has made fundamental contributions to understanding the form and dynamics of Venus and the icy moons of Jupiter. When satellite radar interferometric imaging of earthquake processes became possible in the early 1990s, David had just the skill set to enter this field and make both methodological and fundamental contributions that continue to this day.
He is a master of detail and thoroughness, and the methods he has developed have become standard. Through his selfless generosity he has made both codes and data sets publicly available for wide use by his colleagues. However, David is not primarily a methods person. For example, he developed powerful interferometric synthetic aperture radar (InSAR) analysis tools to enable insightful research exploring fundamental processes of crustal deformation. These include characterizing coseismic rupture, postseismic relaxation, and the nature of interseismic strain accumulation. He recognized the potential of InSAR to capture both fine details of deformation and broad-scale coverage. His group was the first to develop a plate–boundary-zone-wide InSAR data set spanning the San Andreas fault system that, when integrated with GPS, provided the most comprehensive characterization of distributed deformation along this continental transform zone.
One of David’s greatest accomplishments is becoming a truly outstanding scientist while retaining a healthy work-life balance. He is modest and unassuming, living proof it’s not necessary to be a one-dimensional workaholic to be a successful scientist. He is as comfortable on a surfboard as on a keyboard and makes time for his family and his surfing. He is a positive role model to his students, his postdocs, and his colleagues and has left in his wake a trail of happy collaborators from all over the world.
In summary, David Sandwell has, through is research, placed the fields of marine gravity, planetology, and earthquake deformation on a firm quantitative basis; developed rigorous and innovative new methods; discovered hitherto unknown processes; and trained a cadre of graduate students and postdoctoral scholars who now pursue their own research agendas. The arc of David’s career path and his central scientific contributions are nicely described by AGU’s statement of the qualifications for the Whitten Medal, “outstanding achievement in research on the form and dynamics of the Earth and planets.”
—Wayne Thatcher, U.S. Geological Survey, Menlo Park, Calif.
Thank you, Wayne, for this generous citation, and I also thank the scientists who supported this nomination. This is a real honor for an aging geophysicist with some geodetic skills.
As a graduate student at the University of California, Los Angeles, I was fortunate to study under Jerry Schubert, who taught me the importance of physics-based models; Jerry also encouraged my forays into space geodetic data analysis that were inspired by Bill Kaula, Byron Tapley, Dick Rapp, and many other pioneers. Because of their vision and perseverance, we now have tools such as GPS, radar interferometry, and satellite altimetry to study all types of Earth processes at unprecedented spatial and temporal resolutions; these include plate tectonics, ocean currents, and changes in the cryosphere. The past 3 decades have offered a real data feast for Earth scientists, and I was fortunate to be able to help prepare the recipes and be thrilled by the discoveries. I hope we can improve the tools and research opportunities for the next generation.
I began my geodetic career using radar altimeter data from NASA, U.S. Navy, and European Space Agency (ESA) satellites to study the tectonics of the deep oceans. This was a 20-year collaboration with Walter Smith and several talented graduate students. In the late 1990s I began a new research direction to study continental crustal deformation using radar interferometry (InSAR) and GPS. Wayne Thatcher inspired this conversion by taking a sabbatical to learn InSAR from Didier Massonnet and colleagues at ESA. Howard Zebker, Masanobu Shimada, and others at the Jet Propulsion Laboratory, ESA, and the Japan Aerospace Exploration Agency got us started in the development of SAR processing algorithms that utilize precise satellite orbit methods developed by the altimetry community. Paul Segall, Yuri Fialko, and others laid out the models needed to digest the wealth of crustal deformation data provided by GPS and InSAR. All of this relied on the dramatic increases in computer capabilities that we have witnessed over the past 40 years.
Scripps Institution of Oceanography has provided the stimulating intellectual environment and freedom to participate in basic research as well as to train, and learn from, extraordinary students. Moreover, Scripps has one of the best surfing beaches in the world, and as Wayne mentioned, I have often used a midmorning surfing session to clear my thinking. I thank my wife, Susan, who takes care of most of the practical aspects of our life, and also my family, who have tolerated many absences, both physical and mental, that are typical of scientists.
—David Sandwell, University of California, San Diego, La Jolla