Posted on 03/13/2019 9:37:20 AM PDT by Sarcasm Factory
Americans have long dreaded the “Big One,” a magnitude 8.0 earthquake along California’s San Andreas Fault that could one day kill thousands of people and cause billions of dollars in damage. The Big One, though, is a mere mini-me compared with the cataclysm forming beneath the Pacific Northwest.
Roughly 100 miles off the West Coast, running from Mendocino, California, to Canada’s Vancouver Island, lurks the Cascadia Subduction Zone, where the Juan de Fuca Plate is sliding beneath the North American Plate, creating the conditions for a megathrust quake 30 times stronger than the worst-case scenario along the notorious San Andreas, and 1,000 times stronger than the earthquake that killed 100,000 Haitians in 2010. Shockwaves will unleash more destructive force against the United States and Canada than anything short of nuclear war, a giant asteroid strike, or a civilization-threatening super-volcano.
We didn’t even know a megaquake was coming until recently. When I was a kid, growing up in the mid-Willamette Valley in Oregon, earthquakes were California’s problem. Everyone, including scientists, thought us immune. Seismic hazard maps shaded California red and Oregon green. Geologists knew about the Cascadia Subduction Zone, but they thought that the Pacific and Juan de Fuca Plates weren’t locked—that the subduction was smooth, as if the continent were greased with lubricant. University of Washington geologist Brian Atwater proved them wrong in the late 1980s. Oregon had recorded no earthquakes since American pioneers colonized the territory in the nineteenth century, and the native population had no written records, but the earth itself keeps copious records of geologic events, once one knows where to look. Atwater’s first clue was the “ghost forests” along the Oregon and Washington coasts, drowned by seawater, covered by sand and landslide debris, and then exposed by beach erosion. According to tree-ring dating, every one of those forests was buried in 1700. Something extraordinary happened that year. Sea levels can’t rise six or more feet in a year. The coastline itself must have plunged into the ocean. Later, beach erosion exposed yet another ghost forest, in the small town of Neskowin; this one was 2,000 years old.
Atwater then collaborated with Japanese seismologist Kenji Satake, who dug up long-forgotten reports in his own country of an “orphan tsunami”—a violent tidal inundation not preceded by a local earthquake—that also occurred in 1700. Scientists scrambled for core samples of the ocean floor just off the American coast and found turbidites—layers of tsunami debris—that date back millennia and, most recently, again, to 1700, revealing a cycle that repeats itself every 300 to 600 years. The Cascadia Subduction Zone is not quiet, after all: it triggers catastrophic megathrust quakes, on schedule. “A fault that ruptures with this big of an earthquake every few hundred years is ragingly active,” says Yumei Wang, a geotechnical engineer at the Oregon Department of Geology and Mineral Industries (DOGAMI).
A 9.0 megathrust quake is too powerful even to be measured on the now-dated Richter scale. Megathrust quakes are measured instead on the Moment scale. Like its predecessor, the scale is logarithmic. Every whole-number increase represents an energy release 32 times greater than the whole number before it. An 8.0 earthquake is therefore 32 times more powerful than a 7.0, and a 9.0 roughly 1,000 times more powerful.
Of the three West Coast states, Oregon is the most vulnerable. “We’re less prepared here,” says geologic-hazard analyst John Bauer, also at DOGAMI. “Washington has had more earthquakes recently, so they’re better prepared, and California, too, of course. We didn’t adopt a culture of preparation until the mid-1990s.” Portland is also closer to the subduction zone than Seattle or Vancouver, so it will experience more violent ground shaking. And the Oregon coast is considerably more populated than anywhere else in the tsunami’s path. “We’re not overdue,” Bauer says. “But we’re due.”
“Also while I was there we had a 5.7 quake come rolling through one afternoon.”
We felt that one in Grants Pass.
they’ve been predicting the ‘big one’ as beign imminent since the 1960’s why is this prediction so scecial? more chicken little?
Hmmm....guess I’m good. Right now, I’m sitting about 5 miles EAST of I-5, near Tacoma. Even better, when I get home, I’m on a HILL.
Edgar Cayce mentioned, as an aside, that when he would be reincarnated in 2100 or so, it would be in Nebraska, then the west coast of America.
“One of the small Coastal towns in Oregon is doing well in preparation. Besides backup power and water and food they have ordered thousands of body bags.”
1. What do you do with them after they have been bagged? Stack them? Leave them in the bag long enough and they’ll decompose and you’ve got a bag full of...diseased mess. It will probably keep the flys off though. What about animals? Can they tear through the bag to get what’s inside?
2. That doesn’t help me if I’ve got two or three bodies on my front porch/in my front yard as the result of resisting looters trying to take what little I have. Of course I’ll no longer care if one of those bodies is mine, but somebody will.
Never fear. The US and especially CA have been such great stewards of taxpayer money with their careful budgeting, there is plenty of money in reserve such that a disaster of this magnitude will not have a noticeable financial impact.
NOT!!!!
I had just finished a class and a bunch of were standing in a hallway. We could hear it coming and when it hit us it seemed like it lifted the floor 2 feet and slammed it back down. It literally was a roller. No prolonged shaking.
If the date of the earthquake was 1700, that was only several years before the Lewis and Clark expedition of discovery, and the natives surely would have experienced it. Has anyone seen any mention of this in their journals as told to them by the natives?
An even more prudent person living in California would just leave the state entirely.
We only have 12 years...oh wait this really would be climate change!
The year 1700 was more than a century before Lewis & Clark.
“I don’t know who they think is gonna fill them.”
I suspect the “who” will be the dead filling the bags.
(OK the survivors will put the dead in)
Do a search for Oregon Tsunami Map. The state has some pretty good maps to show the extent of the tsunami
To "avoid" the big one? That's like moving to the moon to avoid oxygen deprivation.
Washington state, and Washington DC!
If I know local gubment, all the bags are stored in the new fire department and city hall. They will not be available, should a locally sourced tsunami hit Coos Bay.
“Needless to say, I worry about relatives in California.”
Me too, especially the little children. There would be no way to get to them fast enough if something happened to their parents.
Given you've seen (?) evidence of up thrusting, I wonder how that squares with the article's implication that "ghost forests" are the result of the coastline sinking.
Beats me. I figured it was from the tsunamis. Kfalls is 100× miles inland.
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