“Our operating assumption is that everything west of Interstate 5 will be toast.”
In the Pacific Northwest, everything west of Interstate 5 covers 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.
— newyorker.com
5 Comments
All those walkable neighborhoods with hipster coffee shops will be toast.
Single origin artisan toast?
The possibility of this kind of disaster is a daily reality when you live in the western US, and it's something those in the east (home of the New Yorker) can't understand, that and wildlife management, public lands, natural resources, and a plethora of other issues they like to chime in on. If it's not the Cascadia earthquake disaster, it's the Yellowstone Supervolcano, or The Big One in California, and the incessant wildfires. All parts of natural processes that we have no control over, all these will someday pass, if we're here to actually be disastered upon is less known.
I wouldn't say it would be all toasts.
Depending on alot of things, buildings will perform to varying degrees against the earthquakes.
Where I am, I would not have any major effect by the tsunami itself but only the port areas and certain river front properties (ie. properties right along the river front within a block or so would have river seich (sp?) impact. River seich is the back rippling when the forces of the tsunami and the river goes against each other. The fact is we have these jetties out their which will function to an extent as a breaker wall which will diminish the effects of the tsunami but there would be those rippling up the river like wakes off a tug or big ship but bigger wake-like ripples.
The earthquake itself (and possible aftershocks) is something to be concerned with. Although the earthquake is off the coast and by dozens of miles, the amplitude of seismic energy will be diminished by some degree. However, the intensity of the earthquake would be on the order of Northridge and Landers earthquake but of longer duration but projected ground motion acceleration in terms of G-force is about the same of a California earthquake like Northridge and Landers. This g-force is important factor in consideration of intensity or amplitude of the shaking of buildings which is what causes damages found in earthquakes.
Given also the 1906 earthquake and type of construction of buildings and how they performed during those earthquakes... alot of Astoria downtown buildings are built with similar reinforced concrete construction and they are contained inside glorified concrete boxes of sidewalks and streets. A system of reinforced concrete chair walls. This whole system would be quite reinforced.
It is unlikely there would be total collapse of the reinforced concrete which are in considerable good shape.
However, face brick and other masonry mostly bonded by just mortar can fail and result in masonry falling on the ground around the building. This includes cornices and other systems.
Wood frame construction will usually perform well due to their elastic nature without collapsing but this isn't always true. Especially if you have a stem wall. Balloon frame wall systems will usually perform well and even better than platform frame between floor to floor but if you have a balloon frame over a 'cripple wall' between the balloon frame and foundation walls which are often brick masonry. Although these brick walls will more than likely survive an earthquake due to its mere low wall height, the cripple wall (a intermediary stem wall) are 'hinge points' (creating essentially a 'soft story') which can buckle unless stabilized. Which is why structural reinforcement and connection reinforcement as well as shear walls along the east/west axis would be important to keep the walls from buckling out. This is one of the hallmark type of damage found in many Victorian houses in San Francisco in 1906 and in 1989.
With a CSZ event, seismic waves along the CSZ emanate out away from the fault in a relatively perpendicular direction and mostly along the east/west axis due to the fault line being north/south axis for the most part. North/South axis shear walls maybe needed but are usually going to be secondary shear walls for dealing with smaller local earthquakes. That's an decision determined on a site by site basis.
Some buildings have other issues like being on geological hazard areas known as slide areas and are likely to slide or move and that can result in collapse which requires other stabilization strategies aside from seismic.
Other wood frame construction will likely perform reasonably well due to type of construction such as post and beam construction with wood frame. Hybrid frame and post/beam construction. These buildings can and may perform considerably well provided there isn't geological faults or otherwise soils that will go in different directions underneath. That way, there is a uniform soil geology underneath the entire building or possible settlement issues may arise during the quake when the ground is unsettled by the shake and resettles.
I wouldn't say everything is toast but there will be wide spread damage of many buildings up and down the coast. Some buildings are on geologically stable and competent bedrock and otherwise stable design. Many buildings in Astoria, are largely stable but some have their weak areas. Can they survive such an earthquake? Sure.
Lets remember, the Inca built structures over 500 years ago that have survived the most powerful earthquake ever recorded even after 500 years with zero repair work.... without any rebar. These were dry unreinforced masonry. (ie. no mortar, and no rebar). How statically or close to static stability your building has by design and the walls, columns, and other components is good indication of a stable structure that will likely perform well in an earthquake.
I lived through earthquakes including Northridge and Landers earthquake. I have experienced even the Nisqually earthquake in Astoria. Therefore, I know very well what earthquakes can do and also what performed well and what kinds of structures do not as easily perform as well.
Regarding tsunami, that is an experience I never had and hopefully never have to personally be in myself. The areas most likely affected are the beach line areas and towns along the coast within 3-5 KM. Basically within 3 miles as the tsunami generally do no go in deeper than 2-3 kilometers due to the coastal hills near the beach line along the coast. The biggest thing is once the earthquake is BEING felt, you need to work your way to high ground. That is land above the tsunami peak height or otherwise go beyond the tsunami inundation line by a safe margin like one additional kilometer or up a high hill that is more then 100-ft. high. In Astoria, I'm too far in for a tsunami from a CSZ event to generate a tsunami high enough that will effect me but I'm in business in this community so it matters.
I do foresee massive scale infrastructure disruption ranging from power infrastructure disruption, natural gas, possible internet disruption, other telecom disruption and public utilities.
I do foresee economic strain. I would also foresee a high demand for services after such an event during a period of rebuilding once financial resources become available.
The problem with a west coast disaster is that the east coast will end up paying for it.
Well... sort of. We all end up paying for it. It comes out of taxes but hell, midwest & east coast disasters cost us west coasters all the time (if we want to go by that notion with all the winter storm, hurricanes, ect.) but this is once in 300+ years events based on past patterns but no simple answer to predict.
It is just the nature of the country. Most of the effected area is small towns and cities. Most of the big city is inland a bit so major impacts they would have is minor earthquake damages but usually it would be aging structures like old bridges and some old buildings.
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