It has been centuries since the contiguous United States, all of the states, experienced a “Big One” – an earthquake with a magnitude greater than 9.0. The last recorded was an earthquake in 1700 with an estimated magnitude of 9.0. It was along the Cascadia Subduction Zone where the Juan de Fuca Plate plunges below the North American Plate.
Huge earthquakes occur in this region because the slab that comes down is usually oceanic crust, which is cold and dense, which means it can break suddenly and suddenly.
However, the dense, cold sinking crust can break apart for a much longer period of time and initially lead to seismic shifts and tremors.
The nature of the area associates any earthquake with another destructive event: a tsunami.
The earthquake that struck in 1700 sent a tsunami across the Pacific Ocean to Japan.
Researchers now expect another event in the Cascadia Subduction Zone, the chances of it happening in the next few decades explored during NOVA PBS’s short documentary, “Pacific Northwest is due to earthquake. major land “.
Wendy Bohon, geologist and senior science communication specialist at the Incorporated Research Institutions for Seismology, explained the process behind how a tsunami would result from an earthquake and said, “You have one plate dipping under another, one section locks and it pushes another part up.
“When the rift breaks, when the amount of stress overcomes the friction, it rebounds, which raises the water above it and causes that water to flow in all directions.
“And this water flowing in all directions during the tsunami.”
Oral histories of the earthquake and tsunami that struck in 1700 suggest that many died from the event.
Water has consumed much of the forest and land near the sea, destroying the temporary dwellings of indigenous populations.
However, at the time, Native Americans used the land differently from colonizers, not building any permanent structures and constantly moving through the region.
Now, with a population of millions and structures built to last, things are different.
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The crushing of the plates in the Cascadia area could cause waves up to nine meters high.
These waves would have the potential to immediately kill 11,000 people in states closest to the sea and injure 26,000 others, according to the Federal Emergency Management Agency.
Chris Goldfinger, professor of geophysics at Oregon State University, said the Cascadia area is even more dangerous than the famous San Andreas fault in California.
In 2018, he told CNN: “Cascadia can produce an earthquake almost 30 times as energetic as the San Andreas to begin with, and then it generates a tsunami at the same time, which the side-to-side movement of the San Andreas cannot. not.
“You’re going to have three to five minutes of shaking, and if you’re used to earthquakes in California, they usually last 15 to 30 seconds and before you’re really sure what’s going on, it’s over.”
An analysis in 2016 revealed that there were 43 major earthquakes over the past 10,000 years in the Cascadia area.
These were often over the whole area itself but sometimes over small parts of it.
Then, in November 2017, a study conducted by the University of Texas at Austin found that the occurrence of earthquakes and tsunamis may be linked to compacted sediments along large portions of the subduction zone.
He found that there was a greater chance of a large, destructive earthquake off the coast of Washington and northern Oregon than further south along the subduction zone.
Lead author Shuoshuo Han said, “We observed very compact sediments off Washington and northern Oregon that could withstand seismic failure over a long distance and near the trench, which increases with increasing distance. both earthquake and tsunami risks. “