The earthquake that will devastate the Pacific Northwest

“Everything west of Interstate 5 will be toast.”

____________

Entitled “The Really Big One,” a 2015 article in The New Yorker describes the earthquake that will destroy a sizable portion of the coastal Northwest. Here are excerpts from that article.

Just north of California’s San Andreas fault lies another fault line. Known as the Cascadia subduction zone, it runs for seven hundred miles off the coast of the Pacific Northwest, beginning near Cape Mendocino, California, continuing along Oregon and Washington, and terminating around Vancouver Island, Canada. The “Cascadia” part of its name comes from the Cascade Range, a chain of volcanic mountains that follow the same course a hundred or so miles inland. The “subduction zone” part refers to a region of the planet where one tectonic plate is sliding underneath (subducting) another. Tectonic plates are those slabs of mantle and crust that, in their epochs-long drift, rearrange the earth’s continents and oceans. Most of the time, their movement is slow, harmless, and all but undetectable. Occasionally, at the borders where they meet, it is not.

Under pressure from Juan de Fuca, the stuck edge of North America is bulging upward and compressing eastward, at the rate of, respectively, three to four millimetres and thirty to forty millimetres a year. It can do so for quite some time, but it cannot do so indefinitely.  If only the southern part of the Cascadia subduction zone gives way, the magnitude of the resulting quake will be somewhere between 8.0 and 8.6. That’s the big one. If the entire zone gives way at once, an event that seismologists call a full-margin rupture, the magnitude will be somewhere between 8.7 and 9.2. That’s the very big one.

Everything west of Interstate 5 will be toast

When the next very big earthquake hits, the northwest edge of the continent, from California to Canada and the continental shelf to the Cascades, will drop by as much as six feet and rebound thirty to a hundred feet to the west—losing, within minutes, all the elevation and compression it has gained over centuries. Some of that shift will take place beneath the ocean, displacing a colossal quantity of seawater. The water will surge upward into a huge hill, then promptly collapse. One side will rush west, toward Japan. The other side will rush east, in a seven-hundred-mile liquid wall that will reach the Northwest coast, on average, fifteen minutes after the earthquake begins. By the time the shaking has ceased and the tsunami has receded, the region will be unrecognizable. Kenneth Murphy, who directs FEMA’s Region X, the division responsible for Oregon, Washington, Idaho, and Alaska, says, “Our operating assumption is that everything west of Interstate 5 will be toast.”

The worst natural disaster in the history of North America

In the Pacific Northwest, the area of impact will cover some hundred and forty thousand square miles, including Seattle, Tacoma, Portland, Eugene, Salem (the capital city of Oregon), Olympia (the capital of Washington), and some seven million people. When the next full-margin rupture happens, that region will suffer the worst natural disaster in the history of North America, outside of the 2010 Haiti earthquake, which killed upward of a hundred thousand people. By comparison, roughly three thousand people died in San Francisco’s 1906 earthquake. Almost two thousand died in Hurricane Katrina. Almost three hundred died in Hurricane Sandy. fema projects that nearly thirteen thousand people will die in the Cascadia earthquake and tsunami. Another twenty-seven thousand will be injured, and the agency expects that it will need to provide shelter for a million displaced people, and food and water for another two and a half million. “This is one time that I’m hoping all the science is wrong, and it won’t happen for another thousand years,” Murphy says.

Thanks to seismologist Chris Goldfinger and his colleagues, we now know that the odds of the big Cascadia earthquake happening in the next fifty years are roughly one in three. The odds of the very big one are roughly one in ten. Even those numbers do not fully reflect the danger—or, more to the point, how unprepared the Pacific Northwest is to face it.

We now know that the Pacific Northwest has experienced forty-one subduction-zone earthquakes in the past ten thousand years. If you divide ten thousand by forty-one, you get two hundred and forty-three, which is Cascadia’s recurrence interval: the average amount of time that elapses between earthquakes. That timespan is dangerous both because it is too long—long enough for us to unwittingly build an entire civilization on top of our continent’s worst fault line—and because it is not long enough. Counting from the earthquake of 1700, we are now three hundred and fifteen years into a two-hundred-and-forty-three-year cycle.

osspac estimates that in the I-5 corridor it will take between one and three months after the earthquake to restore electricity, a month to a year to restore drinking water and sewer service, six months to a year to restore major highways, and eighteen months to restore health-care facilities. On the coast, those numbers go up. Whoever chooses or has no choice but to stay there will spend three to six months without electricity, one to three years without drinking water and sewage systems, and three or more years without hospitals. Those estimates do not apply to the tsunami-inundation zone, which will remain all but uninhabitable for years.

Can you imagine the misery and deaths during such a long period of time?

Read the full, and fascinating, article to learn how scientific sleuths dated the last big earthquake (a magnitude-9.0) to strike the Pacific Northwest, and why they think the next one – including a devastating tsunami – is already overdue.

https://www.newyorker.com/magazine/2015/07/20/the-really-big-one

Published in the print edition of the July 20, 2015, issue.

Thanks to Alan for this link


33 thoughts on “The earthquake that will devastate the Pacific Northwest”

    • All the Plates area connected.

      We, talking monkeys, are not smart enough, yet, to determine this.

      In time, with our Science, etc., we will have answers to all this.

  1. Imagine the rioting in the cities like Seattle already subject to lawlessness and demands to defund the police.

    Of course the whole event will be the fault of systemic racism and white privilege !

  2. No Problem

    Just print $5 Trillion as the (PCPP) Pacific Coast Protection Program, make it impossible for anybody to apply, and things will work out great.

    Think of all the materials and machines imported from China that they can use to rebuilt. Built Back Better.

    This will stimulate the Economy…………..of China.

  3. Interesting and inevitable but it doesn’t give the real estate market a moment of pause and seek a reality check does it? Let her rip and the earth movers , clean up and search crews can sort it out after. The public rarely ever learn…

      • Like the days of Noah. The misuse of the rainbow symbol has desecrated the symbol of a holy covenant between god and life on earth so I guess anything is possible.

  4. Seattle Times reporter Sandi Doughton wrote a book on the Cascadia Subduction Zone in 2014. “Full-Rip 9.0: The Next Big Earthquake in the PNW,” is a more detailed look at the information in the New Yorker article. If this topic is of interest, look for a used copy. The science has progressed a lot, but the basic infrastructure issues in Seattle, Portland, etc, remain little changed.

  5. Remember the 7+ in Japan (Fukushima) a few years back? Well, turns out there’s a history of the Cascadia having a Big One withing a few years / decades of Japan having a Big One…

    https://chiefio.wordpress.com/2011/03/15/1707-hoei-49-days-fuji/

    http://en.wikipedia.org/wiki/1707_Hōei_earthquake

    The 1707 Hōei earthquake, which occurred at 14:00 local time on October 28, 1707, was the largest in Japanese history until the 2011 Sendai earthquake surpassed it.
    […]
    http://en.wikipedia.org/wiki/Cascadia_Earthquake

    The 1700 Cascadia earthquake was a magnitude 8.7 to 9.2 megathrust earthquake that occurred in the Cascadia subduction zone in 1700. The earthquake involved the Juan de Fuca Plate underlying the Pacific Ocean, from mid-Vancouver Island in British Columbia, Canada, south along the Pacific Northwest coast as far as northern California, USA. The length of the fault rupture was about 1,000 kilometers (620 miles) with an average slip of 20 meters (22 yards).

    for example. The alignment has some significant variation in which goes first, and exact timing, but there’s a general belief that a “big one” on one side of the Pacific Plates ups the pressure on the other side…

  6. Does anybody have a MAP or good sketch showing the earthquake area and the tsunami area? I live in central coast CA & have been looking for awhile for options for removing myself from the purview of Governor Nuisance.

    • Penelope,
      There is a lot of information available on that sort of thing for CA… much more so than for any other state . The state of CA has it’s own geology site that has that type of info at:
      https://www.conservation.ca.gov/cgs/geohazards.

      For the state also look up Alquist-Priolo Special Studies zones… which is intended to include detailed maps for seismic hazards for all known active faults in the state; any development project is required to assess the site is within a APSS zone…. and if so they are required to conduct site specific studies to identify the level of hazards… No one is allowed to build on any site without checking that (your local planning department should have that information).

      Also, every jurisdiction in CA (county or city) is required to have a Safety Element (sometimes called a Seismic Safety Element) in it’s General Plan and those should be readily available and identify and describe the geological and other natural and man-made hazards (including potential for dam failures) for the jurisdiction. County General Plans tend to have more details as to type of risk in that county, mitigation measures planned, etc. and be a bit more up to date than the local GP… but they should all have maps.

      If you have a look at these things and are having trouble interpreting anything please feel free to contact me at Slosek1@aol.com. I used to be an Environmental Planner in CA (years ago, so a few things may have changed)… and one of my jobs was reviewing Safety Elements and identifying geological and water-related hazards for any proposed projects.

      • Thank you Jean. If I don’t get out of CA I’m going to have to spend some time learning– or factor this info into my decision. Even if Gov Nuisance is recalled it’s a perilous political state.

  7. The other big one, The new Madrid fault with several big earthquakes every 200 years is overdue, That one is much more dangerous. Turning the Mississippi flowing backwards. It can be found everywhere, no one is talking about it.

    • Well people do talk about it.. but what the heck are you going to do about it? NADA.. it’s impossible other than not living there. I lived within the New Madrid hazard zone for years. Worrying about that is like worrying about Yellowstone (and now I live where I would likely die… should the super volcano erupt) …

      Life is full of risks… and every single place on earth has some hazard risk or another… even tho some are more hazardous than others. We should all be aware of that and make our choices of where to live and work based on understanding those and what our individual tolerance level is for the specific type of risk where we choose to live.

      On the other hand there are some monumentally stupid places to live, based on natural hazards. For example, Galveston TX… really awful place to live when it comes to hurricanes. Or Hilo HI, which gets volcanos, tsunamis and typhoons. Or there is this little place in southern VA where the town was build IN the RIVERBED itself… between the river and a steep cliff bank. Gee, they had a storm surge from a hurricane and the whole town was flooded and destroyed… I wonder why?

      Personally, I would never choose to live in a dam inundation area… but lots of people do so. And I would rather live in a place prone to earthquakes than tornadoes. Or some gang-infested inner city neighborhood.

    • I agree. New Madrid is much more likely to happen, and is more frightening as a result.

      And it is not well known among our over-educated young adults. Mention New Madrid and get blank stares. if you throw in junk science and say the earthquake will be caused by global warming, then you get their attention.

  8. In 1964, we were stationed at a USAF surveillance site in the far-west Aleutian Island chain when the Richter 9.4 Alaska Quake generated coastal tsunamis from Anchorage and Oregon to Hokkaido and northeastern Honshu (Japan).

    Fortunately for us, the Aleutians bend in a great arc from North America to Kamchatka’s Petropavlovsk, so Pacific Ocean surges rolled southeast and west. But Anchorage subsided thirty feet, while waves obliterated trans-Pacific enclaves around Latitude 36.

    If North America’s West Coast is in fact 320 : 243 – 1 = 32% overdue for a comparable episode, Lord help all in that 2,000+ mile stretch. Then of course there’s Yellowstone, a slightly overdue disaster, and the southern Mississippi region’s New Madrid fault-line.

    Though dustmote Earth appears hospitable, do not be fooled… as in Lisbon on Easter Sunday 1755, geophysical catastrophe is not the exception but the rule.

  9. I grew up in Humboldt Co, CA. My family was from Petrolia, a tiny little town right on top of the triple junction of the plates. The local indian tribes tell the story of when a tidal wave wiped out the area around Humboldt Bay. Long considered myth it was confirmed some years ago by a group of students from HSU. They were digging in the Arcata Bottoms, a fertile flat plain north of the bay, and discovered tree stumps buried some 12-16 feet below the surface. Eventually it was reasoned that the bay had dropped, in one moment, that far below sea level. Since then, similar locations have been found up the coast all the way to Washington. If you look at the maps, there are several towns, Arcata, Eureka, Ferndale, and Fortuna, that will all be inundated when that big quake finally happens. Depending on the height of the waves, places like McKinleyville, Blue Lake, and down the valley to the south following 101 will also be in danger. I have a lot of family and friends still in the area, I’m not looking forward to that day. I’ve always thought the damage estimates were entirely too low.
    If you look at the USGS fault line maps, they end the San Andreas just a few miles south of the southern tip of the Cascadia. The northern end of the SA used to be around Santa Rosa, Ca. Over the years they keep moving the tip north. IMO they will eventually just acknowledge the obvious and connect the line. It is one gigantic fault line. I think it is possible that a large quake on either end could trigger the other. (As for culling the liberal herd-there are plenty of really good conservatives out there).

  10. M 4.3 – off the coast of Oregon
    Time
    2021-04-29 11:25:16 (UTC+01:00)
    Location
    43.996°N 127.953°W
    Depth
    10.0 km

    M 5.4 – 287 km WNW of Bandon, Oregon
    Time
    2021-04-29 11:30:25 (UTC+01:00)
    Location
    43.863°N 127.817°W
    Depth
    10.0 km

    M 5.2 – off the coast of Oregon
    Time
    2021-04-29 11:35:46 (UTC+01:00)
    Location
    43.886°N 128.282°W
    Depth
    10.0 km

    M 5.3 – off the coast of Oregon
    Time
    2021-04-29 11:58:35 (UTC+01:00)
    Location
    43.918°N 128.038°W
    Depth
    10.0 km

  11. Timely article. last night there were three 5+ quakes and one 4+ quake along the cascadia fault. I haven’t seen that in the several years i have been watching quake maps daily. i live in Humboldt county right at the southern tip of the Cascadia. YIKES.

  12. “Ouch my Balls” *(Idiocracy)
    Good thing we stopped Trojan nuke plant. But my generation is rapidly dieing out anyway. The great Alaska good Friday 9.2 nearly killed this 10 year old! I was bodysurfing in Santa Monica, saw the wave coming, and split before it hit, washing other beachgoers out to sea.
    As a rule the most beautiful places are generally the most dangerous. I no longer live in a subduction zone and Nome Alaska is nothing to look at. I have witnessed 3 volcanic eruptions when living in Homer. The wierd thing about that was, I dreamt it years beforehand before even going there or knowing where my dream took place! So, am I the only person having had tsunami dreams? Doubt that but at least it won’t be like the Rocky & Bullwinkle cartoon intro that Cascadia is faced with. ¶%^)
    P.S. Gnome? Really? One can only hope! And Steven, that’s spelled NOAA.

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