A huge earthquake hit the Northwest 322 years ago today

SPOKANE, Wash.– Exactly 322 years ago, an estimated 9.0 earthquake rocked the Pacific Northwest.

Its existence was unknown, however, to most of the world until less than 50 years ago. The following is an account of how the history of this quake was re-discovered and how it has changed the Northwest forever.

800px How The Richter Magnitude Scale Is Determined

Source: Benjamin J. Burger

On January 26, 1700, a tsunami wrecked coastal villages along the shores of Japan. The island nation is used to earthquakes and tsunamis and has centuries of historical records on them. In Japan, the people knew that the shaking of the earth was often followed by destructive waves.

The word tsunami comes from Japan, translated as “harbor wave” in English. What made this wave unusual is that it had no shaking beforehand. This so-called “orphan wave” had no explanation as to why it appeared when it did.

Across the Pacific Ocean, the oral histories of Indigenous people from California north to British Columbia told a fantastic tale. Not one, but many stories described the shaking earth and mighty waves during a battle between two supernatural beings.

According to the Pacific Northwest Seismic Network: “The Thunderbird and Whale in the Native American stories are creatures of supernatural size and power. Although native myths vary between tribes, the acts and personalities of these supernatural beings in the stories generally describe the effects of earthquake and/or tsunami.”

Oral Histories of PNW earthquakes

Source: Ludwin, Dennis, et. al. (2005) -Dating the 1700 Cascadia Earthquake: Great
Coastal Earthquakes in Native Stories

In some of these histories, however, there were descriptions that were less mythical or metaphorical. Instead, there were stories of previous generations of family that had survived the shaking earth and rushing waters. Taken all together, native histories pointed to a land that was very much earthquake country. As late as the early 1980s, it was believed the Cascadia Subduction Zone, the fault line off the coast of the PNW that was responsible, did not produce earthquakes.

During the 1980s, scientific research revealed exactly the opposite. Soil sampling and tree ring data all but confirmed that a large earthquake (estimated 8.0 to 9.0) and tsunami happened right around the time of the Japanese records of the orphan wave.

The USGS now says that a large “megathrust” earthquake has happened roughly every 400 to 600 years along the Cascadia Subduction Zone. It’s unknown whether these quakes are all of the magnitude 8 to 9 variety or are sometimes weaker. Either way, “the big one” is not just an earthquake term that people need to worry about in California. It is also a clear and present danger to the Northwest.

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