This is the Biggest and Most Damaging Earthquake in Washington’s History


Washington is no stranger to earthquakes. Since 1900, the state has suffered over 100 earthquakes with a magnitude of 4 or higher. However, the largest earthquake to ever strike Washington was the 1700 Cascadia megathrust earthquake, which had an estimated magnitude of 8.7 to 9.2.

What is the Cascadia Megathrust Earthquake?

The Cascadia megathrust earthquake was a huge subduction zone earthquake that struck the Pacific Northwest coast, stretching from northern California to southern British Columbia. A subduction zone is when one tectonic plate slips beneath another, causing a lot of friction and stress. When the plates abruptly move, they release a tremendous amount of energy, resulting in a violent earthquake and tsunami.

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The Cascadia megathrust earthquake occurred on January 26, 1700, at around 9 p.m. local time. The exact date and time are known thanks to historical documents from Japan, where the tsunami generated by the earthquake arrived around 10 hours later. The tsunami also hit the coasts of Oregon, Washington, and British Columbia, although there are no recorded testimonies from Native Americans who lived there at the time.

How Large Was the Cascadia Megathrust Earthquake?

The Cascadia megathrust earthquake was one of the biggest recorded in history. It broke a fault line that spanned approximately 1,000 kilometers (620 miles) from Cape Mendocino in California to Vancouver Island in Canada. The earthquake lasted several minutes and caused strong shaking hundreds of kilometers inland. The earthquake also raised the bottom many meters, moving a large amount of water and causing a significant tsunami.

Geological data and computer simulations suggest that the Cascadia megathrust earthquake will have a magnitude of 8.7 to 9.2. For instance, the 2004 Indian Ocean earthquake, which caused a horrific tsunami that killed over 200,000 people, had a magnitude of 9.1. The 2011 Tohoku earthquake, which triggered a nuclear accident in Japan, had a magnitude of 9.0. The 1964 Alaska earthquake was the biggest in North America, with a magnitude of 9.2.

What Was the Impact of the Cascadia Megathrust Earthquake?

The Cascadia megathrust earthquake devastated both nature and the people that live in the region. The earthquake triggered widespread landslides, liquefaction, and coastal subsidence, altering the contour of the terrain and shoreline. The tsunami swamped and devastated several coastal settlements and woods, killing thousands of people and animals.

The earthquake generated minor earthquakes and volcanic eruptions in the Cascade Range, including Mount St. Helens and Mount Rainier. The Cascadia megathrust earthquake also had long-term consequences for the Native American cultures and histories that survived the tragedy. The earthquake and tsunami were recalled and handed down through oral histories, folklore, and myths.

Some of these myths characterize the earthquake as a struggle between a thunderbird and a whale or as a divine punishment for breaching a taboo. The earthquake and tsunami also had an impact on Native American migratory, trade, and fighting patterns, as well as their interactions with later-arriving European explorers and settlers.

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Final Words

Finally, Washington has seen multiple earthquakes, the most notable of which being the 1700 Cascadia megathrust earthquake. This massive earthquake, with an estimated magnitude of 8.7 to 9.2, changed the region’s geography, causing deadly tsunamis, changing coastlines, and affecting Native American societies. The earthquake’s long legacy lives on in oral histories and myths, creating tales about nature’s strength and its tremendous impact on the Pacific Northwest’s people and ecosystems.

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