M9.2 Alaska Megaquake Could Send 20-Foot Tsunami Waves Toward Washington, New Simulation Shows

Aug 22, 2026

Tsunamis • Alaska-Aleutian Subduction Zone • Washington State

A new Washington Geological Survey simulation shows how a hypothetical magnitude 9.2 earthquake along the Alaska-Aleutian subduction zone could send a powerful distant-source tsunami toward Washington State, with the first waves reaching the outer coast after about 3.5 hours and tsunami energy penetrating deep into Puget Sound.

Simulation graphic showing a hypothetical M9.2 Alaska earthquake sending tsunami waves toward Washington State and Puget Sound — A Washington Geological Survey scenario models how a hypothetical M9.2 Alaska-Aleutian earthquake could send a distant-source tsunami toward Washington, with the first waves reaching the outer coast after about 3.5 hours.

A massive earthquake off Alaska could send a powerful tsunami racing across the northeastern Pacific, slam Washington’s outer coast with waves exceeding 20 feet offshore and push tsunami energy all the way through Puget Sound to Seattle and Olympia.

That’s the scenario explored in a new tsunami model released by the Washington Geological Survey.

And unlike a local Cascadia tsunami, where some coastal communities could have only minutes to reach higher ground, this monster would come from hundreds of miles away.

The first waves would reach Washington’s outer coast just over 3.5 hours after the earthquake.

That sounds like plenty of time.

But the simulation also highlights something easy to forget about tsunamis: the first wave is not necessarily the largest, the danger does not end after the first surge arrives, and destructive currents can continue through harbors, channels and coastal waterways for many hours.

Scientists Simulated a Magnitude 9.2 Alaska-Aleutian Megaquake

The scenario begins with a hypothetical magnitude 9.2 earthquake on the Alaska-Aleutian subduction zone, centered offshore Kodiak Island.

Researchers modeled approximately 65.6 feet (20 meters) of uniform fault slip along the megathrust.

The location was not chosen randomly.

Previous modeling suggested that an earthquake centered in this part of the Alaska-Aleutian system could efficiently direct tsunami energy toward Washington, so scientists deliberately examined a severe scenario useful for emergency planning.

According to the Washington Geological Survey, an earthquake of approximately this size in the modeled region has an estimated recurrence interval of roughly 600 years.

That does not mean another M9.2 earthquake is expected in exactly 600 years or that one is now “due.”

This is a hazard scenario, not an earthquake prediction.

The Alaska-Aleutian arc is part of the much larger Pacific Ring of Fire, where tectonic plates converge around the Pacific Basin, generating many of the world’s largest earthquakes and most active volcanic systems.

For a broader look at how Alaska fits into major earthquake zones worldwide, see our guide to regional seismic systems.

Watch the M9.2 Alaska Tsunami Spread Toward Washington

The simulation shows tsunami energy radiating away from the Alaska-Aleutian subduction zone before crossing the Gulf of Alaska and reaching the Pacific Northwest.

The striking part is not simply that the tsunami reaches Washington.

It is where the water goes once it gets there.

First Tsunami Waves Reach Washington After About 3.5 Hours

The first modeled tsunami reaches waters off Washington a little more than three and a half hours after the earthquake.

That makes this a distant-source tsunami.

It is fundamentally different from a tsunami generated immediately offshore along the Cascadia Subduction Zone.

A major Cascadia earthquake could leave some outer-coast communities with only tens of minutes to evacuate. An Alaska-generated tsunami provides considerably more time for seismic networks to detect the earthquake, tsunami warning centers to evaluate the threat and authorities to issue evacuation alerts.

But three and a half hours is not as generous as it sounds when entire coastal communities may need to move inland or uphill.

And arrival of the first wave does not mean the event has peaked.

The Washington Geological Survey model indicates that tsunami activity could continue for many hours and that the first wave may not produce the greatest inundation.

More Than 20 Feet Near Westport

Washington’s outer Pacific coast takes the brunt of the modeled tsunami.

The simulation produces the largest offshore wave amplitudes near Westport, where they exceed 20 feet (6 meters) above mean high water.

That distinction matters.

It does not mean a uniform 20-foot wall of water would sweep through downtown Westport. Offshore wave amplitude, shoreline water level and inundation depth are different measurements.

Still, the modeled coastal flooding is substantial.

Some of the greatest inundation occurs around Grays Harbor and Willapa Bay, with modeled inundation depths near parts of the shoreline reaching approximately 10 feet (3 meters) before decreasing farther inland.

Low-lying coastal areas, beaches, ports and waterways would therefore face a serious tsunami hazard.

Then the Tsunami Enters the Strait of Juan de Fuca

The tsunami does not simply hit the Pacific coast and disappear.

Wave energy bends around Washington’s coastline and enters the Strait of Juan de Fuca, penetrating the network of channels, islands, bays and waterways behind it.

Eventually, the modeled tsunami reaches both the Canadian border in Whatcom County and Olympia at the southern end of Puget Sound.

News reports examining the model indicate water-level changes of roughly 2 feet around Seattle and as much as 4 feet around Olympia.

Those numbers are far smaller than the wave amplitudes modeled along the outer coast, but tsunami danger is not measured only by vertical water height.

Far inside Washington’s waterways, currents may become the dominant hazard.

Dangerous Currents Could Develop Deep Inside Washington’s Waterways

Tsunamis are dangerous not only because of spectacular waves.

Huge volumes of water forced through narrow passages can generate extremely powerful currents.

The new modeling identifies potentially hazardous tsunami currents around areas including the San Juan Islands, Guemes Channel, Port Gamble and Hood Canal.

Those currents could pose serious risks to boats, docks, marinas and other maritime infrastructure.

A tsunami producing only a few feet of vertical water-level change can still move an enormous amount of water horizontally.

That is why a two- or four-foot tsunami signal should never automatically be interpreted as a harmless “small wave.”

Why Alaska Is a Real Tsunami Threat to Washington

Washington understandably spends a lot of time preparing for the Cascadia Subduction Zone.

But Cascadia is not the state’s only potential tsunami source.

The Alaska-Aleutian subduction zone stretches for thousands of kilometers across the northern Pacific and has produced some of the largest earthquakes ever recorded.

The most famous example occurred on March 27, 1964, when a magnitude 9.2 earthquake struck Alaska.

The earthquake generated a trans-Pacific tsunami that caused damage along parts of the western coast of North America.

Washington Geological Survey notes that the 1964 Alaska tsunami is the only historical distant-source tsunami known to have caused damage along Washington’s coast.

So the new simulation is not based on an impossible geological monster created for dramatic maps.

Earthquakes of approximately this magnitude have happened in Alaska before.

Alaska Is Also One of Earth’s Most Active Volcanic Regions

The same tectonic system responsible for Alaska’s huge earthquakes also feeds one of the world’s most spectacular volcanic arcs.

As the Pacific Plate descends beneath Alaska and the Aleutian Islands, subduction generates both powerful megathrust earthquakes and magma that rises toward the surface.

The result is the long chain of active volcanoes stretching from mainland Alaska across the Aleutian Islands.

You can explore that system in our guide to Alaska and Aleutian volcanoes.

Together, the earthquakes, volcanoes and tsunamis of Alaska provide one of the clearest examples of how interconnected processes along a subduction zone can reshape the surface of the planet.

A Severe Planning Scenario — Not a Prediction

There is an important caveat.

Researchers intentionally positioned the simulated earthquake where previous modeling suggested tsunami energy would be strongly directed toward Washington.

The scenario also assumes the tsunami arrives around mean high water.

As a result, the modeled inundation depths and extents are intended to represent a severe planning scenario rather than a prediction of exactly what the next Alaska earthquake will produce.

Real tsunami impacts would depend on numerous variables, including the exact location and geometry of fault rupture, amount and distribution of slip, tides, currents, coastal topography and local bathymetry.

The model therefore should not be used to predict exactly how deep the water would become at an individual house, road or building.

Its purpose is broader:

What could a very large Alaska-Aleutian earthquake do to Washington’s coastline and inland waterways, and where should communities prepare for the greatest hazards?

Washington Now Has New Tsunami Hazard Data

The project goes considerably beyond producing a dramatic simulation video.

The Washington Geological Survey released statewide modeling showing tsunami inundation extent, inundation depth, arrival times and current speeds.

Researchers and emergency planners can also explore the results through Washington’s Geologic Information Portal.

The detailed model can help emergency managers improve evacuation planning, maritime response strategies, coastal hazard maps, tsunami siren placement and public-warning procedures.

Washington currently faces tsunami hazards from several different geological sources.

Distant Alaska-Aleutian earthquakes can send tsunamis toward Washington with several hours of warning.
Cascadia megathrust earthquakes can generate devastating local tsunamis with far less evacuation time.
Local earthquakes and landslides can generate smaller but much faster tsunami hazards inside regional waterways.

Different source.

Different clock.

Same basic rule: if authorities issue a tsunami evacuation order, move away from the water and follow official evacuation routes.

Frequently Asked Questions About the Alaska Tsunami Scenario

How long would an Alaska tsunami take to reach Washington?

In the Washington Geological Survey’s magnitude 9.2 Alaska-Aleutian earthquake scenario, the first tsunami waves reach Washington’s outer coast a little more than 3.5 hours after the earthquake. Because this is a distant-source tsunami, authorities would generally have much more warning time than during a locally generated Cascadia tsunami.

Could a tsunami from Alaska reach Seattle?

Yes. The simulation shows tsunami energy entering the Strait of Juan de Fuca and propagating deep into Puget Sound. Water-level changes would be much smaller than on Washington’s outer coast, but strong currents could still create hazards for boats, docks, marinas and narrow waterways.

Could an Alaska tsunami reach Olympia?

Yes. The modeled tsunami propagates through Puget Sound all the way to Olympia at its southern end. This demonstrates that distant-source tsunamis can affect inland waterways far from Washington’s open Pacific coast.

Would Westport really experience a 20-foot tsunami?

The model produces offshore tsunami wave amplitudes exceeding 20 feet near Westport. That does not mean a uniform 20-foot wall of water would move through the city. Offshore wave amplitude, shoreline water level and inundation depth are different measurements, although significant coastal flooding is modeled around Grays Harbor and nearby low-lying areas.

Is the Washington Geological Survey predicting a magnitude 9.2 Alaska earthquake?

No. The study is a hazard-planning scenario, not an earthquake forecast. Researchers modeled a severe but geologically possible magnitude 9.2 Alaska-Aleutian earthquake to understand how a major distant-source tsunami could affect Washington.

Why can Alaska generate such large earthquakes and tsunamis?

Alaska lies along the Alaska-Aleutian subduction zone, where the Pacific Plate descends beneath the North American Plate. Large sections of the plate boundary can rupture during megathrust earthquakes, displacing the seafloor and generating tsunamis. The same subduction system also feeds Alaska’s long chain of active volcanoes.