Megathrust Earthquakes

“Civilization exists by geological consent, subject to change without notice. ”
― Will Durant

The Pacific Northwest is home to the Cascadia Subduction Zone (CSZ); a thrust fault capable of producing some of the earth’s most powerful earthquakes and tsunamis.

Stretching from Cape Mendocino, California up to Northern Vancouver Island, British Columbia, the 140,000 square mile area expected to be impacted by a magnitude 9.0 Cascadia Subduction Zone earthquake is home to roughly 15 million people. More than 8 million of those residents are located within Oregon and Washington’s impact area.

When the earthquake and tsunami happen, communications, water and wastewater, food distribution, electricity, natural gas, transportation, and emergency response will all be heavily impacted. Daily life will look all but unrecognizable.

Image from ASCE 7-16 Chapter 6, Tsunami Loads and Effects

by the Incorporated Research Institutions for Seismology (IRIS)

What became known as the Great Chilean Earthquake revealed something new about the planet — that the world itself can vibrate like a guitar stringThe seismic waves went through every part of the globe, even its core. And because they were so strong, scientific instruments from around the world picked up the signal. When it was over, seismologists realized the earthquake had given them a window into Earth’s structure. Nature had given the planet something like an ultrasound scan.

When The Biggest Earthquake Ever Recorded Hit Chile, It Rocked The World

The 1960 subduction zone Chilean earthquake described above was a whopping magnitude 9.5. By comparison, Oregon’s Department of Geology and Mineral Industries (DOGAMI) included a magnitude 9.4 CSZ earthquake as the largest hypothetical earthquake in its research, Variable Rupture Scenarios for Tsunami Simulations Inferred From a 10,000-Year History of Cascadia Megathrust Earthquakes.

To get a better idea of how large these megathrust earthquakes are, check this 2-minute video comparing the magnitude classes.

A magnitude 9.0 earthquake releases the equivalent energy of 480 million tons of TNT—or 30,000 strategic nuclear bombs. It’s massive.

Freund, Friedemann. (2003). Rocks that crackle and sparkle and glow: Strange pre-earthquake phenomena. Journal of Scientific Exploration. 17.

Here’s one more video to help illustrate just how big a magnitude 9.0 earthquake really is.


“Along this fault, three regional tectonic plates—the Explorer, Juan de Fuca, and Gorda plates—are pulling away from the larger Pacific plate and moving toward the North American plate. At the North American plate boundary, these three regional plates are descending—or subducting—underneath the North American plate.”

Cybersecurity and Infrastructure Security Agency’s (CISA) 2021 Resiliency Assessment

“You can, you should, and if you’re brave enough to start, you will.”
― Stephen King

Learning about the earthquake and tsunami that will hit the Pacific Northwest is flat-out scary. Striking without warning, earthquakes are some of the greatest ghost stories ever told. They are nowhere, then suddenly everywhere around us at once, unseen but for the destruction they cause.

“Without fear, there cannot be courage.”
― Christopher Paolini

As you travel along this journey seeking knowledge, as you take steps to prepare yourself and your loved ones, the fear will dissipate. It will transform into determination. Let this website serve as a guide on this journey. You’re here. That, in and of itself, is courageous. You’re taking the first step. Not all those around you will be so brave. Keep learning. Start planning. Prepare. Your loved ones will need you to be ready when the time comes. There is a ghost on our horizon.

How to Navigate This Website

Section 1

Learn what to expect. See how the region will likely be impacted by the earthquake and tsunami.


Section 2

Explore dates of past CSZ earthquakes, take a deep dive into how the risk probabilities are calculated, and see how past intervals tell a different story than the probability figures might suggest.


Section 3

Delve into expected aftermath scenarios in the days, weeks, and months following a significant CSZ event. Learn about co-occurrences between the CSZ and the San Andreas fault, and see why being 2-Weeks-Ready for Cascadia can also help you be ready for other hazards.


Section 4

After the next CSZ earthquake and tsunami, residents in impacted areas of the Pacific Northwest will need to be self-sufficient for at least two weeks. Learn about expected impacts and ways to prepare.


Section 5

Dip your toes into Cascadia’s slow-moving earthquakes which scientists believe add stress to the locked portion of the fault. Explore the frequency and relation of the more minor, offshore earthquakes often highlighted in local news stories. Then take a dive into what challenges a “summer quake” might bring and how to prepare.


Section 6

Check out these other amazing resources. Enjoy the journey and reach out if you have questions, comments, or suggestions!!


CISA 2021 Resiliency Assessment

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