Roger Borcherdt
Roger D. Borcherdt is Scientist Emeritus at the U. S. Geological Survey in Menlo Park, California and past visiting Shimizu and consulting professor at Stanford University. His current major research project is the development of general viscoelastic ray theory as a basis to better understand and interpret seismic wave propagation in anelastic layers of the Earth.
Dr. Borcherdt’s interest in seismology and engineering seismology is manifest in research results documented in more than 200 publications as listed in Google Scholar and ResearchGate. His most significant research since becoming emeritus (2014) is the development of the theory for general viscoelastic rays and head waves from first principles as published in the 2nd edition of his graduate level textbook Viscoelastic Waves and Rays in Layered Media (2020). This theory provides the viscoelastic solutions for forward and inverse ray-theory problems together with general ray-tracing computer algorithms for multi-layered anelastic media ranging from soft soils to mantle and core materials deep within the Earth’s interior. These results explain measurable variations in seismic body and surface waves, such as phase speed, travel time, ray-path location, amplitude attenuation, and particle motion induced by anelastic boundaries in the Earth that are not explained by elastic models. Citations of the textbook reveal applicability of the viscoelastic solutions to a variety of anelastic wave propagation and inversion problems in engineering, seismology, exploration geophysics, acoustics, and solid mechanics.
Dr. Borcherdt’s research interests as documented in publications prior to that of the most recent project include: 1) site-response studies resulting in site coefficients and Vs30 site-class definitions as adopted in national and international building codes and seismic-hazard mitigation maps, 2) mathematical theory of monochromatic wave propagation in layered viscoelastic media as documented in the 1st edition of Viscoleastic Waves in Layered Media (2009), 3) near-source seismic radiation of strain and displacement and its implications for earthquake-fault rupture dynamics as inferred from unprecedented high resolution GEOS recordings of the 2004 M6 Parkfield earthquake, obtained with colleagues, showing no discernible near-field precursory strain or displacement at sensitivities of 10^-11 strain and 5*10^-8 meters, 4) multidisciplinary seismic-zonation and earthquake-loss estimation studies as manifest in initial maps developed with colleagues showing the potential for earthquake intensity (MF-709), surface faulting, ground-motion amplification, and ground failure as prototype maps required by California Law AB-3897 and as extended under the auspicis of FEMA to a national scale in HAZUS, 5) design, construction and deployment with colleagues of the initial central microprocessor controlled wide-dynamic range (180dB) digital strong-motion recording system (GEOS) as a prototype for commercial instrumentation, 6) initial development of US national strong motion instrumentation program to increase public safety by deployments of multiple instrumentation arrays on a national scale to record the response of the built environment to infrequent large damaging earthquakes for purposes of improving the resilience of man-made structures and communities.
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