Reducing Risk where Tectonic Plates Collide –A U. S Reducing Risk where Tectonic Plates Collide –A U.S. Geological Survey Plan to Advance Subduction Zone Science Kristin A. Ludwig, Joan Gomberg, Barbara A. Bekins, Thomas M. Brocher, John C. Brock, Daniel Brothers, Jason Chaytor, Arthur D. Frankel, Eric L. Geist, Matthew Haney, Stephen H. Hickman, William S. Leith, Evelyn A. Roeloffs, William Schulz, Thomas W. Sisson, Kristi Wallace, Janet T. Watt, Anne Wein, Benjamin Brooks, Elizabeth Cochran, Todd Eriksen, Patricia McCrory, and Jessica Murray A blueprint for prioritizing USGS science activities, delineating USGS resources, and partnerships in subduction zone activities. (To be published early June, 2017.)

Science driven by stakeholder needs. land-use planners; civil, structural, and environmental engineers; policy makers; insurance providers; emergency managers and responders; infrastructure operators; business owners; media. E.g., maps that help city officials and engineers prioritize retrofitting of buildings and infrastructure.

A major frontier is to expand the multi-disciplinary and geographic (offshore) scope of monitoring. E.g., adding tremor and slow slip to routine seismic monitoring will not only reduce uncertainties, but may change paradigms! A newly defined tremor distribution in central Alaska indicates the Yakutat plate actively slips over the North American plate (in addition/instead of the Pacific plate). From Wech, 2016.

A major frontier is to expand the multi-disciplinary and geographic (offshore) scope of monitoring. E.g., offshore geodesy may one day provide earthquake warnings of weeks, suggested by precursory slow slip prior to the Tohoku and other earthquakes. From Ito et al., 2013.

Partnering, particularly in offshore infrastructure and new technologies – a priority. USGS partners in developing new offshore technologies.

Already underway - collection & analysis of high-resolution bathymetry offshore and topography onshore, and more precise dating methods. We assume the next major Cascadia earthquake will cause widespread landslides, but no evidence of this exists from previous Cascadia megathrust earthquakes! Dating past individual and episodes of widespread landsliding is challenging, but new approaches using characteristics of the topography to date landslides may hold promise. LaHusen et al. (2015), Geology

Already underway – understanding Cascadia recurrence. Mud and sand deposits offshore have been interpreted as resulting from megathrust earthquake shaking, and to be more frequent going southward. The onshore geologic record does not require this north-south difference. More frequent megathrust earthquakes in the south increases the shaking hazard there by ~40%! onshore tsunami & coastal uplift/subsidence record offshore turbidite & sediment record

Already underway – characterizing PNW faults. UW & USGS are working together to collect high-res submarine data in Lake Washington to improve characterization of the Seattle and South Whidbey Island faults.

Just completed -

Just completed -

Thank you! Questions?