The threat of the ‘Big One’ has loomed over the Pacific Northwest for years.
A powerful earthquake thought to be as large as 9.2 magnitudes ripped through the earth in 1700, along with the 620 mile stretch of the Cascadia Subduction Zone, causing severe shaking and a massive tsunami.
Now, a terrifying new simulation from the Pacific Tsunami Warning Center has plotted the path of the tsunami as it traveled from the US to Japan.
Experts say an event of this kind occurs roughly every 400-600 years, and the area is now overdue for a similar quake that could leave thousands dead or displaced.
In the study, led by a team at the University of Texas at Austin, researchers found that such a quake may be more likely to strike off the coast of Washington and northern Oregon than regions further south along the subduction zone.
Seismic data and sediment samples found that sediments are tightly packed on the plate off the northern sites.
There, little water sits in the pore spaces between the grains, leaving the plates more prone to the build-up of stress.
Under these conditions, the sediments are better able to stick together, and move together in the event of an earthquake – meaning they’re also able to move massive amounts of seawater.
‘We observed very compact sediments offshore of Washington and northern Oregon that could support earthquake rupture over a long distance and close to the trench, which increases both earthquake and tsunami hazards,’ said lead author Shuoshuo Han, a postdoctoral fellow at the University of Texas Institute for Geophysics (UTIG).
Using nearly five-mile-long seismic streamers, the team observed up to four miles of sediment layers lying atop the Cascadia subduction zone.
While the sediments are tightly compacted off Washington and northern Oregon, they’re less compact off central Oregon.
With more pore space between the grains in this area, there would likely be much less stress accumulated there in the event of a rupture, meaning smaller earthquakes.
The higher stress region, however, has the makings for both a large earthquake and a subsequent tsunami.
‘That combination of both storing and more stress and the ability for it to propagate farther is important for both generating large earthquakes and for propagating to very shallow depths,’ said Nathan Bangs, a senior research scientist at UTIG and study co-author.
The ability of an offshore earthquake to propagate to shallow depths is what gives rise to huge tsunamis, such as the devastating wave that hit Tohoku, Japan in 2011 after a magnitude 9.0 earthquake.
According to co-author Demian Saffer, a professor at Penn State University, ‘The results are consistent with existing constraints on earthquake behavior, offer an explanation for differences in structural style along the margin, and may provide clues about the propensity for shallow earthquake slip in different regions.’
Officials in the Pacific Northwest are preparing for such scenes. Seismologists say a full rupture of the 650-mile-long offshore fault running from Northern California to British Columbia and an ensuing tsunami could come in our lifetime. Federal, state and military officials have been drafting plans to be followed when the “Big One” happens.
These contingency plans reflect the potential gravity of the looming disaster: upward of 14,000 people dead in the worst-case scenarios, 30,000 injured, thousands left homeless and the region’s economy set back for years if not decades.
As a response, planners envision an unprecedented deployment of civilian and military personnel and equipment: There would be waves of cargo planes, helicopters, and ships, as well as tens of thousands of soldiers, emergency officials, mortuary teams, police officers, firefighters, engineers, medical personnel and other specialists.
Alex D is a conservative journalist, who covers all issues of importance for conservatives. He writes for Supreme Insider, Red State Nation, Defiant America, and Right Journalism. He brings attention and insight from what happens in the White House to the streets of American towns, because it all has an impact on our future, and the country left for our children. Exposing the truth is his ultimate goal, mixed with wit where it’s appropriate, and feels that journalism shouldn’t be censored. Join him & let’s spread the good word!