In 1700, the Pacific Northwest experienced an earthquake and tsunami event that rivals the 2011 Tōhoku, Japan, earthquake and tsunami. A catastrophic earthquake of this magnitude along the Cascadia fault off the coast of Oregon and Washington is estimated to occur every 500 years. To support Federal Emergency Management Agency (FEMA) and local planners, NISAC analyzed the possible direct and cascading impacts from a magnitude 9.0 earthquake and ensuing tsunami on population and infrastructure. The Japanese incident gave an indication of the results of such a massive event on a heavily populated, urbanized coastal area. Because the last major Cascadia fault event occurred during a time when there was no infrastructure or economy and the population was very small along what is now the U.S. Pacific Northwest coast, a simulation and study was required to project the types and scale of damage resulting from an event of this magnitude occurring today.
NISAC simulated a magnitude 9.0 earthquake along the Cascadia fault, with a tsunami resulting from the earthquake. We then used the ground shaking and tsunami effects to assess the scenario’s infrastructure impacts. The analysis assumes that the disaster event takes place at the current time and proceeds by evaluating human impacts and cascading infrastructure effects within the earthquake impact zone. Finally, we estimated economic impacts. Each of these impact areas (human, infrastructure, and economic) are summarized in the key findings below.
This study first examined the impacts of the earthquake and tsunami on the human population within the affected area. The expected damage and loss of life would occur along the coastal regions of northern California, Oregon, and Washington. The analysis produced an estimate of 3,000 or more fatalities from the tsunami and ground-shaking effects.
Major Infrastructure Impacts
The entire region would experience extensive electrical outages, with medium-term outages forecast for the coastal areas. Restoration is expected to occur on a prioritized basis within one to eight days. Both the natural gas transmission pipeline and the networks of distribution pipelines in the affected region are likely to suffer enough damage for the majority of customers in western Washington and western Oregon to lose natural gas service. Major undersea transoceanic cables are likely to be severed, disrupting communication service to East Asia as well as between Alaska and the contiguous United States, with a two- to three-month expected restoration time.
The total economic impacts are projected to be nearly $70 billion, with nearly $20 billion of that in direct impacts and nearly $50 billion in indirect impacts. Washington State has the largest share (70 percent), with $11 billion in direct and $38 billion in indirect impacts.