GSA Medals & Awards

George P. Woollard Award

David T. Sandwell
David T. Sandwell
Scripps Institution of Oceanography

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Presented to David T. Sandwell

 Citation by Eli Silver

David Sandwell's scientific work is focused on planetary remote sensing, including satellite and shipboard acquisitions of the Earth and radar of Venus. It is for both his scientific accomplishments (including over 100 publications) and his unselfish contributions to the global Earth Science community that he is receiving this award.

Dave's contributions to geological understanding through the use of geophysical tools (the basis for the Woollard award) include his methods for utilizing satellite altimetry and gravity to determine submarine bathymetry for the world's oceans. Prior to this breakthrough discovery (just a few years ago), our knowledge of the ocean floor was patchy, with local well-studied areas set in a broad, poorly resolved (yet sometimes brilliantly interpreted) seafloor. That degree of knowledge was augmented dramatically in short order, so that presently the entire sea floor is known to a fairly high level of detail. Dave's early work with Walter Smith on the southern oceans (the first region to be declassified) showed, for example, the incredible complexity of the spreading fabric between Africa and Antarctica, a region notoriously difficult to study by surface ships. Within a few years the data for the entire world's oceans were declassified, and the exquisite Sandwell and Smith maps of the world were soon made available to anyone for rapid downloading from Dave's website. These maps have revolutionized our ability to carry out global mapping of seafloor evolution. They have also allowed new understandings of the relations between bathymetry and oceanographic processes, such as internal waves, tidal dissipation, and vertical diffusivity.

Not content to simply utilize the fruits of this outstanding discovery for a career of distinguished science, Dave has also become a leading practitioner of InSAR, or interferometric synthetic aperture radar. His contributions to InSAR include discovery of creep events along the San Andreas fault, displaying the 3D deformation field associated with the Hector Mine Earthquake, search for precursory slip on faults, and ground deformation associated with groundwater removal in the LA basin. Following from his deep understanding of InSAR, his most recent work includes the development of Synthetic Aperture Sonar, with the promise of increasing resolution from swath bathymetry and allowing the development of change detection techniques. This effort holds the promise of a far greater level of understanding of seafloor processes. In addition to his work on this planet, Dave has also actively interpreted structures on the surface of Venus using radar imagery. Presently he is senior scientist on the ABYSS Spacecraft proposal for the development of a new satellite altimeter mission to map the marine gravity field to an accuracy of 5 times better than it is known today.

In addition to research, Dave teaches courses in remote sensing, geodynamics, and the physics of surfing (it doesn't hurt that he's also an outstanding surfer). Like his research results, his teaching materials are freely available on his website.

It is a great pleasure to present David Sandwell as the 2004 recipient of the George P. Woollard award. It would have been an even greater pleasure to be here in person to present this citation, but I am presently at sea using tools that Dave is working hard to improve.

 top 2004 George P. Woollard Award - Response by David T. Sandwell

It is an honor and thrill to receive this George P. Woollard award from the GSA. I think Woollard would overjoyed to see gravity measurements become a premiere tool for exploring the remote areas of our planet. I thank Eli Silver and the rest of the committee for nominating me and also for their kind words.

I owe this award to the beauty of plate tectonics and the marvels of engineering physics. Any fool can plot some gravity data to reveal global plate tectonics in all of its glory. I was lucky to be a graduate student under Bill Kaula and Jerry Schubert at a time when NASA still had full control of the earth-orbiter space program. Bill Kaula taught me a number of important things such as: not everyone should be a seismologist; radar altimeter data from GEOS-3 and SEASAT would reveal something new about the Earth; and the southern oceans were largely unexplored. Jerry Schubert taught me to believe in theory, focus on the important issues, and make sure things are correct. Part of this award should go to Walter Smith who, along with Paul Wessel, pioneered the computational tools for the analysis of global data sets. Walter and I have worked closely for more than a decade and we are always pushing each other for better results.

While many awards go to scientists who create theories, we must not forget the teams of creative scientists and engineers who develop our measurements systems. For example, I challenge you to think of a measurement that does not rely on GPS for positioning or time transfer. My award today relies on radar altimetry, which at first glance appears to be a simple measurement. However, consider that a range precision of 3 centimeter is needed to achieve a gravity field accuracy of 3 milligal over the ocean. How can this work when the ocean surface is covered by 3-m tall waves and the satellite is moving at 7000 m/s? What about the tides and currents and atmospheric delays? All of this magic was created by scientists and engineers who usually don't receive awards.

This award would also not be possible without the beauty and simplicity of plate tectonics. Back in graduate school at UCLA we studied a book edited by Allan Cox called "Plate Tectonics and Geomagnetic Reversals". The book contains chapters by famous scientists such as Hess, Wilson, McKenzie, Morgan, and Parker showing pictures of rigid plates sliding across a slippery mantle driven by convective escape of heat from the Earth. I had diagrams of plate boundaries consist of ridges, transforms, and subduction zones all neatly organized to fit on a sphere. As skeptical scientists we don't really believe our own models and as a student, I thought plate tectonics was simply an abstract description of a more complex process. Well I was wrong and gravity data helped to confirm that the simple descriptions of plate tectonics especially in the deep ocean basins. I think Woollard would be astounded and satisfied if he could look at the marine gravity field today.