Disaster scenarios provide insight into society’s disaster vulnerability that structural analyses and catastrophe risk models do not (and vice versa). The USGS Science Application for Risk Reduction (SAFRR) program constructed the SAFRR Tsunami Scenario, a hypothetical event resulting from an Mw 9.1 Alaskan earthquake, to help California communities with disaster planning. The tsunami would have far greater impact on California than did 2010 Chile or 2011 Tohoku. Among these are 1800 census blocks with flooded buildings; $5 to $10 billion in repair costs and business-interruption losses; 1/3rd of coastal small craft damaged or sunk; damage and several days of downtime for shipping, piers, and cargo; fire at marine oil terminals; and scour damage to important roads and bridges. In collaboration with facility stakeholders (port officials, US Coast Guard, Caltrans engineers, county emergency managers and others), scenario writers identified a variety of options to enhance resiliency, either through strengthening measures, emergency planning activities, or recovery strategies. Among these are lengthening dock pilings to accommodate tsunami heights; changes to tsunami messaging protocols to increase warning time; and redundant and flexible operating capacity at coastal ports. The scenario produced new techniques and procedures, such as preliminary tsunami fragility functions for small craft, estimating the regional economic impacts from tsunami damages, and disruption and examining the effectiveness of economic resilience strategies. It highlighted some research needs, such as the economic impact from evacuating the maximum tsunami zone, and economic impacts and resilience at the local scale. A social-science assessment of the scenario process revealed that hundreds of scenario consumers such as facility operators and emergency managers found the scenario credible and plan to use it to improve their tsunami risk-management decisions.