Citation by Breanyn MacInnes
I am pleased to convey the citation for the 2025 Kirk Bryan Award of the Quaternary Geology and Geomorphology Division to Alan Nelson and co-authors for the paper titled “A maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages for coastal evidence of megathrust earthquakes and tsunamis” published in Quaternary Science Reviews in 2021.
This paper pulls together a wide range of records of large earthquakes and tsunamis in southern and central Cascadia and applies improved geochronology techniques. The authors employ careful and detailed analysis of field data and stratigraphy, complex and cutting edge statistical analyses of radiocarbon age results and clearly explained logic to compute a maximum rupture model. This is no black-box analysis—their data and thinking are transparent and clearly expressed, with the data freely available in the paper and as a supplement so anyone can recreate their work and see their reasoning. They also do not gloss over problematic results but present the range of data and discuss issues with their dataset.
The result is 16 robust dates for Cascadia earthquakes from the last 6,700 years, with revised recurrence intervals and strong support for limited-extent Mw 8 as well as larger Mw 9 earthquakes. Their conclusions are critical for accurately estimating the Cascadia slip budget and their work has become a key study for the National Seismic Hazard Model.
Cascadia has benefited from a generation of researchers at dozens of field sites, resulting in one of the world’s most detailed paleoseismic histories. The large author list, extensive bibliography, the shocking number of radiocarbon dates used, and the many field sites all reflect a culmination of decades of work. As a researcher working on other subduction zones, reading Nelson et al. (2021) is like a dream of what could be achieved elsewhere to understand subduction zone behavior globally. It exemplifies the next-level synthesis possible once enough foundational data exist—and shows the value of carefully re-evaluating legacy data using modern techniques.
Finally, this paper represents Alan Nelson’s long career, collaborations, and mentorship, the latter of which is embodied in the diverse author list spanning a wide range of expertise and career stages. Congratulations to Alan and his colleagues for the well-deserved Kirk Bryan Award.
Response by Alan Nelson
As the ringleader of our research team, I am more than honored to accept the 2025 Kirk Bryan Award for our 2021 paper in Quaternary Science Reviews. Thank you so much, Bre, for your kind, humbling, and—in the QG&G tradition—appropriately brief citation. Many thanks also to those who wrote letters supporting her nomination, and to the QG&G Division awards panel for recognizing, for the third time, the work of Cascadia’s paleoseismology community. To quote Ellen Wohl, the 2009 winner of this award, “It is particularly gratifying when people who are always busy go out of their way to recognize the work of others.” Having made and supported previous nominations for this award, I understand its place in the history of North American Quaternary and geomorphology studies. For this reason, you can imagine my utter amazement on learning that our paper had been selected for this year’s award.
As Bre notes in her citation, in our analysis of the earthquake history of the central and southern parts of the Cascadia subduction zone we had the benefit of hundreds of radiocarbon ages collected over 34 years. Little of this dating would have happened without three decades of support from the USGS Earthquake Program, the National Science Foundation, and in the early years, from the U.S. Nuclear Regulatory Commission to several USGS scientists. Craig Weaver with USGS in Seattle, aided for many years by his chief lieutenant Brian Sherrod, was a tireless supporter of coastal paleoseismology studies at Cascadia, even during years when uninvolved self-appointed experts pronounced the major questions about Cascadia earthquake history to have been answered. During the first decades of this research, Brian Atwater’s indefatigable enthusiasm for coastal earthquake studies inspired many of us. Most recently, we thank USGS researcher Kate Scharer for her earlier paper about the San Andreas fault, which provided us with a maximum-rupture-model framework to follow in our paper.
Personally, I gratefully acknowledge the example of excellent science set by my PhD advisors, John Andrews, who received this same award when he was less than half my age, and Giff Miller, the second author of the paper honored with the award last year. I also thank my Masters advisor, Dave Mickelson, for showing me what field research is all about. Coastwise, I have learned even more over almost three decades from working with coauthors Harvey Kelsey and his former PhD student, Rob Witter. My Cascadia studies also benefited from interacting with and scrutinizing the work of scientists studying Holocene sea level in northwest Europe, particularly Ian Shennan, Michael Tooley, and Orson Van de Plassche. This led to my unbelievably fortunate and productive collaboration at Cascadia with co-author Ben Horton and his many top-notch, fun-loving students, two of whom are also coauthors. Many USGS scientists also furthered my four-decade paleoseismology career at USGS, a few include Lee-Ann Bradley, Steve Personius, Tony Crone, Mike Machette, Bob Bucknam, Rich Briggs, and coauthor Chris DuRoss.
On behalf of all Cascadia paleoseismologists, our team thanks the QG&G Division of GSA for recognizing the scientific and societal importance of our work.