by Mary Harrsch © 2025
Today I read that almost 1000 employees of NOAA who operates both of the U.S. tsunami warning centers were fired.
Here in Oregon, we have been experiencing increasing numbers of earthquakes triggered as
the result of movement within the Cascadia Subduction Zone which lies just offshore. This is a major geological fault where the Juan de Fuca tectonic plate is being forced beneath the North American plate. The Cascadia Subduction Zone is capable of producing very large earthquakes, often referred to as "megathrust" earthquakes, capable of producing tsunami waves reaching as high as 100 feet.
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Although not a tsunami, this wave of the Pacific crashing against the sandstone bluffs of Shore Acres near Coos Bay, Oregon reached a substantial height without impetus from a mega quake. A subsequent wave almost washed me and a friend off the cliff in the foreground that is about sixty feet above the ocean. For those of you into digital image editing, I transformed my photograph with Topaz Impression using the Van Gogh II preset with customized adjustments. To create the flecks of foam I shortened the stroke width. I also adjusted the orange, yellow and green channels and decreased the contrast significantly to make the shape of the wave more visible. I added a slight vignette then in Photoshop removed some of the flecks around the edges using a healing brush. Photo by Mary Harrsch |
Here are the regional and global implications of such an event according to DeepSeek:
"A major megathrust earthquake along the Cascadia Subduction Zone would have catastrophic consequences for the Pacific Northwest and broader Pacific region. Here's a breakdown of the projected damages and impacts:
1. Local Impacts (Pacific Northwest Coast):
Ground Shaking:
The earthquake, likely in the range of Magnitude 8.5–9.0 or higher, would cause intense shaking lasting several minutes. This would result in widespread damage to infrastructure, including:
Collapse of buildings, bridges, and highways, especially older structures not built to modern seismic codes.
Damage to ports, airports, and railways, disrupting transportation and supply chains.
Destruction of utilities like water, gas, and electricity lines.
Tsunami:
A megathrust earthquake would displace the ocean floor, generating a massive tsunami. Waves could reach 30–100 feet (9–30 meters) in height along the coast, causing:
Flooding and destruction of coastal communities, including cities like Astoria, Newport, and Seaside in Oregon, and parts of Washington and Northern California.
Loss of life and injuries, as evacuation times may be limited (tsunami waves could reach the coast in as little as 15–30 minutes).
Damage to coastal ecosystems, fisheries, and marine infrastructure.
Economic Impact:
The economic toll would be immense, with estimates ranging from tens to hundreds of billions of dollars in damages. Key industries like fishing, tourism, and shipping would be severely disrupted.
Humanitarian Crisis:
Thousands of people could be killed or injured, and many more displaced. Emergency services would be overwhelmed, and recovery could take years or even decades.
2. Regional Impacts (Pacific Northwest):
Landslides and Liquefaction:
The shaking could trigger landslides in mountainous areas and liquefaction in low-lying, water-saturated soils, further damaging infrastructure and homes.
Inland Flooding:
Rivers and estuaries could be affected by the tsunami, causing flooding far inland.
Displacement of Populations:
Large-scale evacuations and long-term displacement of residents from coastal areas would strain resources in inland communities.
3. Broader Pacific Impacts:
Tsunami Across the Pacific:
The tsunami generated by the earthquake would radiate across the Pacific Ocean, affecting coastlines thousands of miles away. Countries like Japan, Hawaii, the Philippines, and others could experience significant wave heights, leading to:
Coastal flooding and damage.
Disruption of shipping and maritime activities.
Potential loss of life and economic impacts in distant regions.
Global Economic Disruption:
The Pacific Northwest is a critical hub for trade and commerce. Damage to ports like Seattle and Portland could disrupt global supply chains, particularly for industries like agriculture, technology, and manufacturing.
Environmental Impacts:
The earthquake and tsunami could cause long-term environmental damage, including contamination from destroyed industrial facilities, oil spills, and damage to marine habitats.
4. Preparedness and Mitigation:
Efforts are underway to improve preparedness, including:
Strengthening building codes and retrofitting critical infrastructure.
Developing early warning systems for earthquakes and tsunamis.
Educating the public about evacuation routes and emergency plans.
However, the scale of a Cascadia megathrust event would still overwhelm existing systems, highlighting the need for continued investment in resilience and disaster response.
In summary, a Cascadia megathrust earthquake would be one of the most devastating natural disasters in modern history, with profound local, regional, and global consequences."
Here in Oregon, we are strengthening building codes and retrofitting critical infrastructure guided by research at Oregon State University's O. H. Hinsdale Wave Research Laboratory. I am a bit perplexed, though, by the lack of education of the general public about this. We had a tsunami alert just a few months ago and there was widespread confusion about where to go for safety despite numerous evacuation route signs. Coastal residents have now been encouraged to make trial runs to the designated safety location for their area. However, coastal residents reaching enough elevation or a vertical structure constructed to withstand a 100-ft tsunami is deemed "challenging" at best. DeepSeek explains:
"Residents of the Oregon coast could potentially reach sufficient elevation in the Coast Range to survive a 100-foot tsunami, but this would depend on several factors, including their location, the time available for evacuation, and the condition of evacuation routes. Here’s a detailed analysis:
1. Elevation in the Coast Range:
The Coast Range in Oregon has elevations ranging from 500 to 4,000 feet, well above the height of even a 100-foot tsunami. If residents can reach the foothills or higher elevations within the Coast Range, they would be safe from the tsunami.
2. Time Constraints:
Tsunami Arrival Time:
After a Cascadia megathrust earthquake, a tsunami could reach the coast in as little as 15–30 minutes. This leaves very little time for evacuation, especially for those living directly on the coast or in low-lying areas.
Earthquake Impacts First:
The intense ground shaking from the earthquake itself would cause immediate chaos, damaging roads, bridges, and infrastructure, and making evacuation efforts even more difficult.
3. Distance to the Coast Range:
The distance from the coast to the foothills of the Coast Range varies:
In some areas, the foothills are just 5–10 miles inland, which could be reachable by car or even on foot in an emergency.
In other areas, the distance might be greater, making evacuation more challenging.
4. Evacuation Routes and Challenges:
Road Conditions:
The earthquake would likely damage or destroy critical roads and bridges, making it difficult or impossible to drive inland. Landslides and liquefaction could further block routes.
Traffic Congestion:
In the event of a mass evacuation, roads would quickly become congested, slowing or halting progress. Panic and confusion could exacerbate the situation.
Accessibility:
Not all coastal residents have easy access to roads leading into the Coast Range. Some may need to rely on local high ground or vertical evacuation structures instead.
5. Realistic Survival Strategies:
Given the challenges, the most realistic survival strategies for coastal residents include:
Local High Ground:
Many coastal communities have identified nearby high ground that can be reached on foot within minutes. This is often the best option for immediate survival.
Vertical Evacuation Structures:
In areas where high ground is not easily accessible, vertical evacuation structures (e.g., reinforced buildings or tsunami shelters) are being developed. These structures are designed to withstand both the earthquake and the tsunami, providing a safe haven for residents who cannot escape inland in time.
Community Preparedness:
Coastal communities are working to improve tsunami preparedness, including:
Building vertical evacuation structures.
Educating residents about evacuation routes and safe zones.
Conducting regular drills and exercises.
6. Conclusion:
While it is theoretically possible for coastal residents to reach sufficient elevation in the Coast Range to survive a 100-foot tsunami, the practical challenges of time, distance, and damaged infrastructure make this difficult for many. The most effective strategies for survival are:
Moving to local high ground immediately after the earthquake.
Utilizing vertical evacuation structures where available.
Following community evacuation plans and participating in preparedness efforts.
Ongoing efforts to improve infrastructure, education, and emergency response are critical to enhancing the chances of survival in the event of such a catastrophic event.
Are the safe zones currently designated high enough to withstand a 100-ft tsunami wave?
The safety of designated tsunami evacuation zones in the Pacific Northwest depends on their elevation and distance from the coast. While many existing safe zones are designed to protect against more common tsunami heights (e.g., 20–50 feet), a 100-foot tsunami wave would pose a much greater challenge. Here's an analysis of whether current safe zones are adequate:
1. Current Safe Zones:
Elevation Requirements:
Most designated safe zones are located at elevations of 50–100 feet above sea level, which is generally sufficient for tsunamis in the 20–50 foot range. However, a 100-foot tsunami would require safe zones to be at least 100–150 feet above sea level to ensure safety, depending on the local topography and wave dynamics.
Distance from the Coast:
Safe zones are often located within a few miles of the coast, on nearby hills or bluffs. While this is practical for quick evacuation, it may not provide enough elevation for an exceptionally large tsunami.
2. Challenges with a 100-Foot Tsunami:
Inundation Depth:
A 100-foot tsunami would inundate low-lying areas far inland, potentially reaching elevations previously considered safe. Communities and infrastructure located even at moderate elevations could be at risk.
Wave Energy and Debris:
The force of a 100-foot tsunami would carry massive amounts of debris, which could damage or destroy structures even at higher elevations. Safe zones would need to be not only high enough but also reinforced to withstand such impacts.
3. Vertical Evacuation Structures:
To address the limitations of natural high ground, many coastal communities are investing in vertical evacuation structures. These are specially designed buildings or towers that can withstand both earthquake shaking and tsunami forces. Key features include:
Elevated Platforms:
Designed to be above the predicted tsunami inundation zone, often at heights of 100 feet or more.
Reinforced Construction:
Built to resist earthquake damage and the impact of tsunami waves and debris.
Accessibility:
Located within easy reach of coastal populations, allowing for quick evacuation.
Examples of such structures include schools, government buildings, and standalone towers designed specifically for tsunami evacuation.
4. Regional Variations:
The adequacy of safe zones varies by location:
Northern Oregon and Washington:
Some areas have steep coastal terrain that provides natural high ground at sufficient elevations. However, low-lying areas like Long Beach, Washington, or parts of Seaside, Oregon, are more vulnerable and rely heavily on vertical evacuation structures.
Southern Oregon and Northern California:
These regions often have lower-lying coastlines, making it harder to find natural safe zones at the necessary elevations.
5. Ongoing Efforts and Improvements:
Recognizing the threat of a 100-foot tsunami, communities and governments are working to improve evacuation plans and infrastructure:
Updating Hazard Maps:
Tsunami inundation maps are being revised to account for worst-case scenarios, including 100-foot waves.
Building More Vertical Evacuation Structures:
Funding and construction efforts are underway to increase the number of vertical evacuation options.
Public Education:
Communities are being educated about the risks and the importance of reaching high ground or vertical structures quickly.
Conclusion:
While many current safe zones are adequate for smaller tsunamis, a 100-foot tsunami wave would exceed the capacity of some designated areas. However, ongoing efforts to build vertical evacuation structures and update hazard plans are helping to address this gap. Coastal residents should familiarize themselves with local evacuation routes and safe zones, and prioritize reaching high ground or vertical structures as quickly as possible after an earthquake. Preparedness and infrastructure improvements are critical to saving lives in the event of such a catastrophic event."
I live in the Willamette Valley, east of the protective Coast Range Mountains and where most of the larger cities in Oregon are located. However, even here, devastation from an earthquake exceeding 8.0 would be widespread. DeepSeek lists the challenges for those of us living inland:
"The Willamette Valley, located inland from the Oregon coast, would not be directly impacted by a tsunami wave, even one as large as 100 feet, because it is shielded by the Coast Range mountains. However, the region would still face significant indirect consequences from a Cascadia megathrust earthquake and tsunami. Here's a breakdown of the potential impacts:
1. Seismic Damage:
Ground Shaking:
The Willamette Valley would experience strong shaking from a Cascadia megathrust earthquake, potentially causing:
Damage to buildings, bridges, and infrastructure, especially older or poorly constructed structures.
Disruption of utilities like water, electricity, and gas.
Damage to roads and railways, complicating transportation and emergency response.
Liquefaction:
Parts of the valley, particularly areas with loose, water-saturated soils (e.g., near rivers), are susceptible to liquefaction. This could lead to:
Sinking or tilting of buildings and infrastructure.
Damage to underground utilities and pipelines.
2. Population and Economic Impact:
Influx of Evacuees:
The Willamette Valley, home to major cities like Portland, Salem, and Eugene, would likely become a refuge for evacuees from the coast. This could strain resources, including:
Housing, food, and medical supplies.
Emergency services and healthcare systems.
Economic Disruption:
The earthquake and tsunami would disrupt key industries in the valley, such as agriculture, manufacturing, and technology. Supply chains for goods and services could be severely impacted.
3. Infrastructure and Services:
Transportation Disruptions:
Damage to highways, bridges, and railways connecting the valley to the coast and other regions would hinder the movement of people and goods. For example:
I-5, the major north-south corridor, could be damaged or blocked.
Airports like Portland International (PDX) might face operational challenges.
Utility Outages:
Power outages, water shortages, and communication breakdowns could last for days or weeks, affecting residents and businesses.
4. Long-Term Recovery:
Rebuilding Efforts:
The Willamette Valley would play a central role in the long-term recovery of the region, serving as a hub for coordinating relief efforts and rebuilding infrastructure.
Economic Shifts:
The economic focus of the region might shift temporarily toward disaster recovery and reconstruction, impacting other industries.
5. Psychological and Social Impact:
The trauma of the earthquake, combined with the influx of displaced coastal residents, could have lasting psychological effects on the population. Community support systems and mental health services would be critical.
Conclusion:
While the Willamette Valley would not face direct tsunami impacts, it would still experience significant challenges from a Cascadia megathrust earthquake. The region's role as a refuge and recovery hub would be vital, but its infrastructure, economy, and social systems would be tested. Preparedness, including strengthening infrastructure and emergency planning, is essential to mitigate these risks."
I assume the type of damage a megathrust quake would produce here would occur in countries on the other side of the Pacific as well. Are the residents of the west coast "blue" states considered expendable by the current regime?
