The Big One
Updated: Aug 23
Satellite image of west coast of North America along which Cascadia subduction zone stretches for over 700 miles. Credit: NASA/ISS
On January 26, 1700, a magnitude-9.0 earthquake struck the Pacific Northwest, now known to be along the Cascadia Subduction Zone. According to a study, the odds of a big (magnitude 8.0-8.6) Cascadia earthquake happening in the next fifty years are roughly one in three. The odds of the really big one (magnitude 8.7-9.2) are roughly one in ten.
The Cascadia Subduction Zone spans 700 miles north-to-south, off the coast of Oregon and Washington. The Ring of Fire is actually a string of subduction zones that create the largest-magnitude earthquakes in history, known as “megathrust” earthquakes.The next big earthquake in the Cascadia Subduction Zone could have a Magnitude as high as 9.2.
If a large Cascadia earthquake and tsunami occurred today, FEMA estimates that it will cause nearly 13,000 fatalities and 27,000 injuries, and will damage more than a million buildings and cause a million people to be displaced from their homes. Jumpstart’s Resilience Report found that housing displacement has the potential to be the most severe consequence of a major earthquake.
Cascadia Region Earthquake Workgroup, also known as CREW, talks about some far reaching impacts of the earthquake and tsunami in their report. It says that the significant impact in the eastern parts of the zone will be indirect. Eastern cities and airports, such as Redmond, Oregon, and Spokane and Moses Lake, Washington, may become staging areas for emergency resources and personnel.
Eastern areas will also be affected economically by damage to western roads and bridges, ports, and the Columbia River navigation system, which will prevent the normal movement of goods, including the export of agricultural products. Disruption of the fuel distribution system may cause shortages in some inland areas, such as southeastern Washington. Because the region’s economy is interconnected, less damaged eastern areas are also likely to be affected by economic changes on the west side, including the loss of numerous small businesses in quake-damaged areas, the possible exodus of some large businesses out of the region, and the decline in tourism, particularly along the coast.
The earthquake is expected to sever major undersea trans Pacific cables, which would substantially disrupt communications between the United States and East Asian countries. Rerouting communications traffic around the affected area may produce delays and disruption elsewhere in the United States. The tsunami-inundation zone will remain basically unlivable for years. The entire Pacific Northwest will face a long-term economic down-turn and loss of population.
CREW and emergency management and scientific agencies across Cascadia have been engaged for years in public education efforts aimed at raising awareness and encouraging individuals, families, and businesses to prepare for earthquakes and tsunamis. These efforts include coordinated “drop, cover, and hold” earthquake drills (www.crew.com). FEMA maintains a website (www.ready.gov) as part of a campaign to educate the public and help people prepare for emergencies, including earthquakes. The National Weather Service’s TsunamiReadyTM program helps communities on the coast plan and prepare for potential tsunamis.
A Cascadia Subduction earthquake will impact an estimated 140,000 square miles, an area nearly as large as the size of California. The impacted area will include the large metropolitan cities Seattle, Tacoma, Portland, Eugene, and both State Capitals of Oregon (Salem) and Washington (Olympia) - and around seven million people. FEMA projects that nearly thirteen thousand lives could be lost in the Cascadia earthquake and tsunami. Another twenty-seven thousand will be injured, and the agency expects that it will need to provide shelter for a million displaced people, and food and water for another two and a half million.
We might not be able to avoid or contain an earthquake and tsunami of this impact; but we can be prepared. From the most vulnerable to the socially secure and powerful - every individual and community has to be brought together. The good news is that resilience planning and mitigation strategies are being prioritized, says the CREW report. The states of Washington and Oregon have completed resilient state plans. These efforts brought together experts and stakeholders to assess the current seismic vulnerability of a variety of key sectors, including critical and emergency services, transportation, utilities, communications, and finance and business. The initiatives identified state level priorities and produced frameworks and recommendations for increasing each state’s resilience over the next 50 years. While the initiatives focused on the earthquake hazard, many of the strategies and recommendations they produced would improve resilience in relation to other hazards as well.