The Oregon Resilience Plan (2013) [pdf]
oregon.gov
oregon.gov
Lots of smaller bridges are going to come down. I don’t know why there isn’t more focus on them. They should be easier to retrofit. And at least have one in each area that will stay up to keep city connected. For example, I live near hospital but it is on other side of freeway and have no idea if will be reachable.
Every other bridge has been touched since the 80s/90s, but I don't have a lot of faith that, say, the Steel or Hawthorne will stay up.
Regular commute and business traffic would disappear, of course.
None of those things are true for the Columbia River separating Oregon and Washington. There aren’t many bridges and they’re very long. The river is non-trivial to cross. That would be a big mess.
(many bridges would have to go down for this to be the only way, of course)
I figure equipment to unload boats might be damaged, but the boats themselves should be able to come and go as before, no?
The result is that most buildings in Portland will survive. Only unreinforced masonry and liquefaction areas will have serious damage. The quake is survivable, the problem is infrastructure wasn't built with quake in mind.
The Oakland-San Francisco Bay Bridge was damaged in the quake, though other crossings: the Golden Gate, Dunbarton, San Mateo, Richmond-San Rafael, Carquinez Strait, and Martinez bridges, all survived intact.
Suspension bridges are also far more resilient than fixed (truss, viaduct) spans, though several of the structures that did survive are fixed designs.
Which is why word "rediscovered" was working hard in my earlier comment, rather than merely loitering as some may have suspected. Whilst there was some ferry service prior to the quake, existing route service was expanded greatly, and new routes added:
"Water Emergency Transportation Authority | Draft Final Transition Plan"
The Alameda/Oakland Ferry Service (AOFS) was started after the Loma Prieta earthquake on October 17, 1989, in direct response to the collapse of a section of the San Francisco-Oakland Bay Bridge and the nearly month-long closure that followed. the evening of the earthquake, private excursion vessel operators moved people across the Bay. By the following Monday, emergency funding had been secured and ferries were being operated between the San Francisco ferry Building, Oakland’s Jack London Square, and a temporary terminal at the foot of Main Street in Alameda. After the Bay Bridge was reopened, ferry service operated by Red and White Fleet and sponsored and funded by the city of Alameda, Port of Oakland, MTC and CalTrans was continued....
Vallejo’s current-day ferry service started in 1986 when Red & White fleet started limited commuter ferry service to and from San Francisco and midday service to marine world, which had just opened.... After the Loma Prieta earthquake in 1989, ferry ridership increased dramatically and remained high for several years. In 1994, the city of vallejo purchased their first high-speed ferry boat...
<https://weta.sanfranciscobayferry.com/sites/weta/files/weta-...>
A more general history at Wikipedia notes that Oakland, Alemeda, Berkeley, Richmond, and Treasure Island service all post-date the Loma Prieta quake: <https://en.wikipedia.org/wiki/Ferries_of_San_Francisco_Bay>
Living in California, we get public service announcements and outreach about preparedness. The FEMA guidelines of 3 days supplies are a fine rule of thumb for a lot of disruptive scenarios. I personally feel a 2 week ability to "shelter in place" is about the best one can hope for. But all of those rely on the underlying detail that should some great disaster hit an area like Southern California, that there is a large amount of infrastructure and support outside of the area that can be marshaled and rallied to support those impacted by the event.
Simply put, within 2 weeks, not only has the cavalry arrived, you're likely already on your way out to a safe area.
Mind, I live in a earthquake zone. My singular true risk is uncontrolled fire. Modern, wood stick frame housing is very resilient and resistant in collapse in case of a large quake. It can condemn the house, but the house will not likely crush the occupants.
But fire, well fire is fire. We, unfortunately, know far too much about the disaster potential for fire. So, my hope is that at worse the house gets broken, doesn't catch on fire, and someone will show up within 2 weeks helping me get to someplace else. Other than that, just gotta wing it.
2 weeks of random soup and beans from a can is not a hard thing to stock up. Water is a trick if you're not doing it consciously, but it's not up to the rafters with supplies if you do.
Oregon, however, is just not so lucky. If they get their planned for monster earthquake, it's very likely help will not be able to arrive within 2 weeks. You're likely looking at a much more apocalyptic scenario rated at several months. If anything, you should prepare to start hiking out.
The infrastructure impact seems to be very high in Oregon. Even nearby help may not be able to get to you, with the roads being in utter ruin.
So all I can hope is that there is effective outreach to the folks in Oregon and some solid advice shared on how to potentially cope with these events should they happen. Because Oregon has different issues and the generic guidelines likely will not be successful in this case.
Realistically, I’m already pushing 50, so if the quake happens, I might hope to be crushed in the rubble instantly rather than starve over the ensuing weeks. The longer it takes for the quake to happen, the higher the probability I will.
One big problem with walking to safety is that the bridges along the highways will be out. Plus, a lot of people will have the same idea. Most of the official help from central Oregon will be focused on helping western Oregon and not on refugees.
Finally, you are missing route for the supplies: the river. It should be possible to clear the fallen bridges and open the ports. Ships can provide a lot more aid than trucks.