I am pleased and honored to present the 2021 William Gilbert Award to Richard Blakely for fundamental work revealing the structure of active plate margins and for outstanding service to the Geomagnetism, Paleomagnetism, and Electromagnetism (GPE) community.

Rick has rigorously applied potential theory of magnetic and gravity fields to the structure and processes of active plate margins. His early research on magnetic anomalies caused by sea-floor-spreading provided more detailed information about the geomagnetic dynamo and the geologic processes that enable high fidelity recording of the geomagnetic signal by the oceanic crust. At the USGS, Rick has made a major impact on our understanding of subduction zone processes and hazards. His sustained effort to map the upper plate structure of the Cascadia subduction zone with high resolution aeromagnetic surveys now covers over 150,000 square km and is still ongoing. This work has revolutionized our ability to map crustal structure in the tectonically active, but heavily forested Cascadia margin. He has documented the structures that accommodate northward migration and clockwise rotation of the upper plate inferred from paleomagnetic and geodetic data, and he has provided a road map for prospecting for active faults in the heavily urbanized forearc. This data also provided Blakely evidence for a magnetic mantle wedge, interpreted to be serpentinized peridotite produced by fluids coming off the subducting slab and a controlling factor in subduction zone earthquakes.

In an earlier life as a professor at Oregon State, Rick realized the need for a textbook on gravity and magnetic applications that bridged the gap between classic texts on potential theory and those on practical geophysics. His textbook, written in his off hours (when he was not cartooning the quirks of earth scientists or fly fishing), has thousands of citations. It has become a standard for practitioners of potential-field methods and students in graduate-level courses around the world.

Rick Blakely's outstanding commitment to AGU shows through his leadership and service to the GPE community and the Union, serving as President and Secretary of GPE, as an Associate Editor of AGU journals, and as chair of awards, budget, and search committees.

In recognition of his international reach as a scientist and educator and his unselfish service to GPE and AGU, we congratulate Richard Blakely, the recipient of 2021 William Gilbert Award.

Ray E. Wells

U.S. Geological Survey, Portland, Oregon

AGU Member, GPE, Tectonophysics Sections

Thank you, Ray, for your kind words, and thanks to the Geomagnetism, Paleomagnetism, and Electromagnetism (GPE) nominating committee for believing I am deserving of this honor. I am truly humbled looking back at the list of former Gilbert Award recipients. Those of you who know my work will know it would not have happened without collaboration with many colleagues. I regret that space allows me to mention only a few: Ray Wells, Brian Sherrod, Craig Weaver, and Tom Brocher working on tectonics and earthquakes of the Cascadia subduction zone; and Bob Simpson, Bob Jachens, Tom Hildenbrand, Jon Glen, and Vicki Langenheim, members of a strong cadre of potential-field USGS geophysicists in Menlo Park, California. Finally, I am forever grateful for the unflagging support of my wife, Diane. I was lucky that Bob Butler convinced Alan Cox to take me on as a Stanford PhD student. The luck continued when the USGS hired me to work on the fledgling Wilderness Program. The USGS gave me the freedom to apply potential-field methods to diverse geologic problems of the Western US. Within the USGS we formed GUMP, a robust gang of potential-field geophysicists in Menlo Park. I also was privileged to serve as President of the GPE Section during a time of AGU transition. A particular watershed moment came in 1992, when we were funded to try an experiment: use aeromagnetic data to map concealed, active faults in the forested volcanic terrane beneath Portland, Oregon. Using our USGS airplane, we flew a modest survey to locate the Portland Hills fault. That led to three decades of mapping and characterizing active structures of the Cascadia convergent margin. The timing could not have been better; it coincided with the acquisition of high-resolution lidar topography and the development of dense GPS networks that revolutionized our understanding of Cascadia deformation. It was 50 years ago to the month that I gave my first AGU presentation! It was in a GP session (E had not been added yet) in a tiny backroom of the old Jack Tar Hotel in San Francisco. My talk was a disaster, as I recall, but I clearly remember the warm friendship and mutual respect amongst the attendees, notably Subir Banerjee, Rob Coe, and Ron Merrill. That collegial atmosphere has not dwindled, and I have always considered GPE to be my professional home in AGU. Thank you all again for this wonderful honor. Richard Blakely, U.S. Geological Survey