The Cascadia subduction zone in the Pacific Northwest is the area highlighted in the study. It is geologically similar to northern Japan’s seismic region, and the two areas can even be considered “geologic mirror images” of each other. In Japan, the oceanic crust of the Pacific Plate moves westward and slides under the continental crust of the Eurasian plate, which contains the islands of Japan. In the Pacific Northwest region, the oceanic crust of the Juan de Fuca Plate is moving east and slides under the continental crust that makes up Oregon, Washington, and northern California. By examining sediments in coastal marshes and the ocean floor, scientists have been able to compile a historical record of major earthquake and tsunami events in the Pacific Northwest. The most recent occurred over 300 years ago in 1700 AD, when a magnitude 9.0 earthquake struck the region and generated a massive tsunami. According to the study and based on this historical list, the likelihood of the occurrence of a Cascadia earthquake in the next 50 years is 7 to 15% for a great earthquake (magnitude 8.7 to 9.3) and 37% for a very large earthquake (magnitude 8.3 to 8.6). This prediction exemplifies the need for earthquake preparedness.
The report, entitled “The Oregon Resiliency Plan: Reducing Risk and Improving Recovery for the Next Cascadia Earthquake and Tsunami,” states that in the event of a 9.0 earthquake and subsequent tsunami in the region, the following scenarios could unfold: significant fatalities could occur, ranging from 1,250 to 10,000; tens of thousands of homes and buildings could suffer tremendous damage, requiring months to years of repair work; more than $30 billion in USD would be necessary for handling direct and indirect economic losses; more than one million dump truck loads of debris as a result of the earthquake damage to infrastructure would be created; disruption of liquid fuel accessibility would be inevitable; and potentially crippling economic and population declines for many years after the disaster. The plan suggests undertaking massive preparations so as to be ready for an earthquake. These recommendations include taking inventory of buildings and transportation needed for emergency response and for maintaining critical services, conducting risk assessments for water systems and utilities, changing rating systems for building safety, and creating risk communication and education programs for the public.
Photo source: FEMA News Photo. The photo was taken after the Northridge Earthquake of California on January 17, 1994. Approximately 114,000 buildings were damaged during this earthquake and 72 deaths were reported. Many building code changes were enacted after the destruction from this earthquake.
For discussion on earthquake preparedness on the east coast of the United States, please see: