OPB’s Aftershock

Oregon Public Broadcasting (OPB) has an incredible amount of information pertaining to Cascadia Subduction Zone earthquakes. I highly recommend watching the OPB Unprepared documentary.

One of my favorite items is their Aftershock Widget. Normally, you can use the widget to enter your city (or even exact coordinates) & the page will return information about what to expect in the aftermath of a 9.0 earthquake. The widget is currently not working well and I have just learned OPB plans to retire the widget. Here are screenshots from their page comparing expectations for Neskowin (coastal city), Salem (valley city), and Bend (city east of the Cascades).

Based on the figures in the screenshots above, here are the durations that the Willamette Valley is expected to go without water, sewer, electricity, and natural gas. The figures are much longer in the coastal region.

Below, check to see what intensity level a city has. Then scroll through the slides to read about that level’s expectations. There are two slides for level 5: one for coastal locations and one for inland locations.

Many who read the famous New Yorker article by Kathryn Schulz that stated everything west of the cascades would be toast, stopped wondering what the area east of the mountain range would be like. In fact, many people assume the eastern cities won’t be impacted.

Note that even cities located in the FAR east of Oregon are expected to experience level 2 intensity with things falling off shelves while windows and dishes break. I have yet to find a city with a level 1, so I don’t have information pertaining to what that would look like. My assumption at this point is that you’d have to be as far east as Idaho to experience a level of shaking that low. The widget only covers Oregon.

I have heard several people say that when the big one hits, they are going to head east over the Cascades to Bend or Redmond. Redmond is, in fact, preparing for millions to flood into its city as refugees. If you’ve had the chance to view the Oregon Department of Human Services’ Office of Resilience and Emergency Management’s 2022 Able Readiness exercise (I highly recommend doing so!), you’ll note that some people will be airlifted out of the region. Most won’t.

A quick MapQuest search shows a journey on foot from Salem to Redmond takes over 51 hours to complete. You’d need to somehow carry enough food, water, medical, sanitation, and sheltering supplies to make it. Could you and your loved ones do that in below-freezing temps? What if you or a loved one are injured in the shaking? It’s going to make the walk that much harder, even on the sunniest of days.

More, Redmond and Bend will have their own infrastructure issues to deal with. They will struggle to provide medical care, housing, food, sanitation, and other supplies to the influx of that many people. Please take this information into consideration when you and your family are creating your emergency plan.

This next bit of info isn’t from OPB, but the data is relevant. According to the 2021 Oregon Health Authority’s Cascadia Tsunami Casualty Estimates report, here are the expected number of fatalities.

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The report states, “Casualty estimates, which combine injuries and fatalities, are assumed to occur within hours of the earthquake (as opposed to days after the earthquake). Estimates, which include permanent residents and visitor populations, are for a summer “night” (i.e., 2 AM) when visitor populations are high. It is important to note the modeling assumes that all persons quickly evacuate by foot using the most optimal tsunami evacuation route; these estimates are not a worst-case scenario.”

The image raised some questions about why the north is predicted to experience so many of the casualties. Are the figures based on population? I did some digging. Based on 2020 census data, there isn’t a huge difference in population between the north and south.

The coastal cities listed above are color-coded by county with northern counties at the top and southern at the bottom.

As with most things, the casualty estimates are multi-faceted. Topography appears to play a major role, as does access to evacuation routes and tourist flows. If you are traveling to the PNW coast, please make sure you know your evacuation routes! Practice them. Time how long it takes to make it from your favorite places to the safe zones. Does it take longer on stormy days? Are there roads and bridges that may fail in an earthquake, making the route more difficult?

Have you checked out Oregon State University’s O-Help page to see if the area will be prone to landslides or liquefaction, possibly making routes more difficult? Do you have a backup route in mind? Will you be with children, or elderly or disabled persons? It can take as little as 30 minutes to plan and practice. Those 30 could save your life. Check out the tsunami evacuation maps to get started.