A magnitude nine (M9) earthquake along the Cascadia fault would cause immense shaking, liquefaction, and trigger landslides and tsunamis from British Columbia to northern California. The resulting losses would cost tens of billions of dollars and thousands of human lives. The University of Washington’s M9 Project is working to address the scientific and engineering challenges in reducing this risk.

The challenges start with assessing the range of distributions of fault motion and, therefore, the shaking and tsunamis that the Cascadia fault might generate. The project addresses factors not previously considered, including the distribution and timing of energy release on the fault, the coherent variation of frequency content of fault motion with fault depth, and the 3D effects of the deep basins along Puget Sound—and will specify the uncertainty in the estimated motions, which is critical to probabilistic estimation of earthquake impact, including liquefaction, landslides, tsunamis, and built infrastructure response.

The project will develop new probabilistic, statistical, and numerical methodologies to provide deeper insight into these phenomena. The project’s research will improve forecasting of landslides and liquefaction through better resolution of the underlying physics with recent data from Japan and Chile. It will also improve estimation of tsunami effects by developing more realistic scenarios of seafloor deformation and by estimating the battering power of entrained debris. Built-environment response to the unique long-period and long-duration ground motions will be evaluated probabilistically using advanced numerical simulation. To inform the development and deployment of earthquake early warning in the U.S., the project includes interview and survey research on the potential effects of messages that provide just a few seconds or minutes of warning. With local communities and agency partners, the project will improve the utility of probabilistic information by comparing how stakeholders interpret (a) single “worst case” hazard scenarios and (b) multiple probabilistic scenarios, and how each type of scenario is then incorporated into community emergency preparedness and long-range planning. The project will also advance the integration of probabilistic assessments into hazards education.

The last decade has provided unexpected lessons in the enormous risks from giant subduction earthquakes of M9. Sumatra 2004, Chile 2010, and Japan 2011 each caused devastation that took scientists and residents by surprise. M9 earthquakes in the Cascadia subduction zone pose the greatest natural hazard in the Pacific Northwest and provide an integrative focus for interdisciplinary research on reducing future losses to extreme events. To address challenges in risk reduction, this project brings together experts from academia, government, and other nonprofit organizations. The shared vision is to reduce the catastrophic risk of a Cascadia M9 earthquake through integrated advances in forecasting, warning and adaptive planning across the social, built and natural environments. The project will move beyond generalized scenarios toward probabilistic predictions of M9 seismic events and the subsequent hazards, with the objective of integrating these into community resilience planning and advancing the state of earthquake early warning systems.

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