Cascadian Megaquake Resilience: Difference between revisions
| Line 5: | Line 5: | ||
= Projected Impact = | = Projected Impact = | ||
Oregon state officials forecast an earthquake that would last 4 to 6 minutes, followed in as little as 15 minutes by a tsunami. | |||
The earthquake would likely drop areas along the coast by several feet below sea level. The combination of lower elevations and the action of the earthquake could send tsunami surges of up to 80 feet above sea level into coastal areas and also flood the estuaries of the Columbia, Willamette and other rivers. | The earthquake would likely drop areas along the coast by several feet below sea level. The combination of lower elevations and the action of the earthquake could send tsunami surges of up to 80 feet above sea level into coastal areas and also flood the estuaries of the Columbia, Willamette and other rivers. | ||
Revision as of 15:40, 27 July 2023
Cascadia, the bioregion defined by Pacific Ocean to the west + Cascade Mountains to the east, is long overdue for its next megaquake.
These earthquakes (megaquakes = > magnitude 8) have happened on average every ~250 years for at least 10,000 years.
Projected Impact
Oregon state officials forecast an earthquake that would last 4 to 6 minutes, followed in as little as 15 minutes by a tsunami.
The earthquake would likely drop areas along the coast by several feet below sea level. The combination of lower elevations and the action of the earthquake could send tsunami surges of up to 80 feet above sea level into coastal areas and also flood the estuaries of the Columbia, Willamette and other rivers.
Fatalities could top 25,000 with tens of thousands of buildings destroyed, highways collapsed, electrical and other utilities broken and communications knocked out. The total economic loss would likely be more than $30 billion, making it the most expensive "natural disaster" in U.S. history.[1]
Some of the major cities along the length of the Cascade Volcanic Arc include Portland, Seattle, and Vancouver, and the population in the region exceeds 10 million. All could be potentially affected by volcanic activity and great subduction-zone earthquakes along the arc.[2]
Worst-Case Scenario
The more catastrophic scenario is for a 9.0 earthquake along the entire zone from Canada to the California border. That would destroy much of the infrastructure west of the Cascades, according to state and federal officials. In a 2015 New Yorker magazine article on a possible Cascadia earthquake, Kenneth Murphy, who then directed the Federal Emergency Management Agency Region 10, responsible for Oregon, Washington, Idaho and Alaska, said, “Our operating assumption is that everything west of Interstate 5 will be toast.”[3]
Emergency Preparedness
Oregon
The Cascadia Playbook is a 100-page outline of actions to be taken in the first hours and days after the disaster, issued by the State of Oregon in 2018. The playbook covers the first two weeks after an earthquake. Bend would be the center of the state’s emergency response in the worst-case scenario.
Oregon hopes to implement a $12 million statewide earthquake and tsunami early warning system by 2023. The plan is for it to link up with existing and planned warning systems in California and Washington to offer a regional alert.[4]
The Office of Emergency Management is also working with local governments, community groups and the American Red Cross on a $1.6 million plan to ensure that 250,000 homes in the earthquake zone have a two-week supply of water, food, medicine and other supplies in place by 2021.
The state also plans to spend $11.1 million to develop “more robust logistical staging bases,” according to the governor’s proposed budget.
“When the next Cascadia subduction zone earthquake strikes the Pacific Northwest, Oregon will face the greatest challenge of our lifetimes,” Gov. Kate Brown said in a statement in October. “Oregon’s buildings, transportation network, utilities, and population are not as ready as they should be and we must accelerate our preparations.”[5]
Willamette Valley
The Willamette Valley is sitting on sediment, and if an earthquake hits, the highways may not be drivable. Because of this, the Redmond Municipal Airport may be the closest area not directly affected. The airport is being upgraded to be the command post for the state if the earthquake happens off the coast of Oregon.
Central Oregon will be an important aspect of supporting the emergency in the Valley, but "we get the majority of our commodities via the I-5 corridor," he said, which includes fuel. "Almost the entire state of Oregon gets all their fuel through a fuel hub in Portland that's not anticipated to survive the Cascadia earthquake, so getting things like fuel, supplies, groceries, power..." will not be possible for days, weeks or months.[6]
Just Transition
Historic Quakes
The most recent Cascadian megaquake struck on January 26, 1700, with an estimated magnitude of 8.7–9.2.[7]
Seismology
Cascadia Subduction Zone
It has only been in the past 25 years that scientists have begun paying close attention to the Cascadia Subduction Zone. It’s about 50 to 75 miles off the coast of Oregon where two of the earth’s geological plates meet — the Juan de Fuca plate is slowly folding under the Turtle Island plate, creating the Cascade Mountains and all the volcanoes within the mountain range.[8]
"The Cascades themselves are about 40 million years old, so this has been a volcanically active area for a long time," said Julie Donnelly-Nolan, a geologist with the United States Geological Survey. "Then if you just think really much more recently, the peaks that we see every day vary in age, but [are] somewhere from tens of thousands of years old to hundreds of thousands of years old."[9]
The zone stretches from the west coast of Vancouver Island in the north to just off Eureka, California, in the south.
Sources
- ↑ https://www.bendbulletin.com/localstate/bend-is-worse-case-scenario-command-center-in-major-earthquake/article_0503ff13-835c-56af-99e2-db82e5f27f91.html
- ↑ https://en.wikipedia.org/wiki/Cascade_Volcanoes
- ↑ https://www.bendbulletin.com/localstate/bend-is-worse-case-scenario-command-center-in-major-earthquake/article_0503ff13-835c-56af-99e2-db82e5f27f91.html
- ↑ https://www.bendbulletin.com/localstate/bend-is-worse-case-scenario-command-center-in-major-earthquake/article_0503ff13-835c-56af-99e2-db82e5f27f91.html
- ↑ https://www.bendbulletin.com/localstate/bend-is-worse-case-scenario-command-center-in-major-earthquake/article_0503ff13-835c-56af-99e2-db82e5f27f91.html
- ↑ https://www.bendsource.com/news/apocalypse-when-16113015
- ↑ https://en.wikipedia.org/wiki/1700_Cascadia_earthquake
- ↑ https://www.bendbulletin.com/localstate/bend-is-worse-case-scenario-command-center-in-major-earthquake/article_0503ff13-835c-56af-99e2-db82e5f27f91.html
- ↑ https://www.bendsource.com/news/apocalypse-when-16113015