Professor Emeritus Robert (Bob) Crosson passed away on April 29, 2025 at the age of 86.

Bob received an undergraduate degree in geology from UW in 1961. After completing his Ph.D. at Stanford, Bob returned to UW as a geology faculty member in 1966 and later joined the new Geophysics Program in 1969. Bob was a dedicated teacher, and he carried out most of the early teaching in the Geophysics Program. His breadth of knowledge in seismology was incorporated into his classes, which included many aspects of geophysics.

One of the first seismologists to be hired at UW, Bob was the founder of the Pacific Northwest Seismic Network, which was then called the Washington Seismograph Network. With a grant from the National Science Foundation, Bob hired a technician and bought the equipment for an eight-station telemetered seismic network in western Washington. The first two stations started recording on paper and film in 1969 and by mid-1970 there were enough stations installed (6) to start locating earthquakes in the central Puget Sound region.

Scott Crosson, Bob’s son, fondly remembers tagging along in the field with his father while in grade school in the late 1960s and early 1970s, setting up stations in an old, abandoned mineshaft or cascade tunnel. With partly collapsed entrances and cave-ins, he said that while “it was probably something my mom would not have approved of…my dad always assured our safety, and we never had any accidents.”

Besides overseeing the station installations, Bob developed a simple 3-layer crustal velocity model and simple location technique to start an earthquake catalog of local events. His first publication using data from this network was on the structure and tectonics of the Puget Sound region published in 1972. In the same year, Bob arranged for the U.S. Geological Survey to install the first volcano monitoring stations on Mount St. Helens, Mount Rainier and Mount Baker. Bob expanded on his knowledge by doing research on the seismicity of Kilauea volcano in Hawai’i during his first sabbatical leave. His interests further broadened to include tectonics, particularly the study of subduction zones.

Bob developed a coda-duration magnitude scale for the Pacific Northwest that was used up until 2012, when modern calibrated seismometers made routine amplitude magnitudes more reliable. He developed one of the first techniques for inverting earthquake arrival times for both the velocity structure and earthquake locations. His early velocity model is still used today (with minor adjustments). As the seismic network grew to cover all of Washington and into Oregon, Bob continued to do cutting-edge research using its data, and to support student projects. Even after his retirement in 2004, he stayed active for several years investigating the newly discovered seismic tremor along the subduction megathrust.

“It’s impressive to think how Bob’s original effort has grown into such an important enterprise that both sustains the science with observations of new earthquakes while also contributing to public safety and awareness,” says department chair David Schmidt.

Bob was known for the care he took in his research and in mentoring his students. The small seismic network Bob started has now grown to over 700 stations supported by a staff of over 25, and covers all of Washington and Oregon. This advancement is, in part, because of Bob’s foresight and care for high-quality work.

“My dad had an insatiable curiosity about things that I think guided him in his work and in life in general. We had so many great times. Our family was truly lucky to be guided by such a man as my father,” said Scott.

Bob and his wife, Mary Alice, generously created an endowment that provides ongoing support for our graduate students.