The Power of Megathrust Earthquakes

The 1960 earthquake listed above was a whopping magnitude 9.5. A quote from a National Public Radio (NPR) piece titled, “When The Biggest Earthquake Ever Recorded Hit Chile, It Rocked The World” reads:

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.

Again, the 9.5 was the largest ever recorded earthquake. 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.

What kind of impacts could the earthquake have on the Pacific Northwest? One significant impact will be on infrastructure. The Oregon Seismic Safety Policy Advisory Commission (OSSPAC)’s Oregon Resilience Plan lists expected times for the restoration of services. *Oregon assessment only*

Washington State Department of Natural Resources paper, Modeling a Magnitude 9.0 Earthquake on the Cascadia Subduction Zone off the Pacific Coast shows some of their expected outcomes.

Table 1. Summary of significant losses in the M9.0 Cascadia subduction zone earthquake scenario. *Washington assessment only*