The Cascadia Subduction Zone may be unique...

The Cascadia Subduction Zone (CSZ) may be unique among the world's subduction zones in that it produces very few earthquakes precisely on the zone boundary. Based on evidence of past great megathrust earthquakes, the CSZ must be much more strongly locked than other subduction zones. It's not clear whether the entire CSZ always ruptures in great Magnitude 9 (M9) earthquakes, or whether smaller M8 or M8.5-sized events also can break parts of the zone in between the full rupture events. Great! Just great!

http://pnsn.org/outreach/earthquakesources/csz

City of Cannon Beach, Oregon Tsunami Evacuation: Pedestrian Route Maps

The City of Cannon Beach has prepared pedestrian evacuation route maps that can be utilized in case of a tsunami generated by a local Cascadia Subduction Zone earthquake, or a tsunami generated by an earthquake far from the Oregon Coast.

The purpose of the maps is to complement the Tsunami Evacuation Map that has been prepared by the Department of Geology and Mineral Industries (DOGAMI) for Cannon Beach by providing more specific information to City residents and visitors on evacuation routes.

The City has been divided into ten areas. To find the evacuation route map for your area of interest, select the Evacuation Route (ER) from the key on the Index Map.

For each route map, there is a designated assembly area where evacuees can safely wait for the all clear signal. The City is working to establish supply caches in conjunction with the designated assembly areas.

Use the maps to help plan your evacuation route from your home or business. Your goal should be to reach the designated assembly area, or a location that is landward of the yellow line on the map, within 15 to 20 minutes of an earthquake.

If you have suggestions for changes or improvements, please contact Mark Barnes, City Planner from the Planning Department at
barnes@ci.cannon-beach.or.us, or (503) 436-8040.

How to Survive a Tsunami Handout [.pdf]

Cannon Beach Evacuation Route Map Presentation [.pdf]

August-December 2014 "Walk the Evacuation Routes" Schedule [.pdf]

Link to the City of Cannon Beach webpage

Sea-Floor Sunday #20: Cascadia Subduction Zone - from Wired.com

Sea-Floor Sunday #20:

Cascadia Subduction Zone

by Brian Romans

Science 6/1/2008 for Wired.com

I guess I'm on a plate tectonics kick. The last few Sea-Floor Sundays have shown bathymetric (sea-floor topography) images at a scale where big-scale tectonic features are evident (see Scotia Plate, regional context of Chaitén volcano, and Gulf of California).

For today, I wanted to show a nice image of the Cascadia Subduction Zone offshore of the Pacific Northwest of the United States. First, the map (below) shows the relatively small Juan de Fuca plate and associated subduction zone for context. The Juan de Fuca plate is subducting from west to east under northwestern United States and southwestern Canada.

(© USGS)

As sea-floor mapping technology continues to improve researchers continue to learn more about submarine geology. As the resolution and coverage gets better we are able to investigate regions across a broad range of scales.

Coastal areas are mapped much more thoroughly than the open ocean because of their importance to human livelihood (and proximity for operations). As a result, many of Earth’s continental-oceanic plate boundaries are relatively well-imaged. The image below is from a paper I’ve discussed before by Pratson & Haxby in 1996 (link to paper here). This only shows bathymetry seaward of the continental shelf edge – all the black area in the upper left is the submerged continental shelf and coastline. The view is to the south and shows the Oregon part of the subduction zone.

The first thing that jumps out in this image is the belt of folds and faults that runs the length of the subduction zone in this area. This is mostly sedimentary material that is getting crumpled up as the plate subducts (from right to left on image above). As accretionary wedges go, this one is pretty dang accretionary! In fact, you can’t even see an obvious trench seaward of the fold-thrust belt. This area is so swamped with terrigenous sediment (i.e., derived from continent) that its filling in any low spot it can get to. Note the relatively flat areas between the worm-like ridges – these are basins filling with sediment. One reason why ancient accretionary wedges are so difficult to figure out is that sedimentation and deformation are occuring at the same time, which results in mind-bendingly-complex relationships.

Also note the beautiful submarine valley heading out seaward of the continental slope onto the less-deformed oceanic plate. Even though you can’t quite see it (off the bottom left of the image), you can imagine that a sediment pathway has developed cutting through the entire accretionary wedge. That’s a fun story to save for another time.

Link to this article online

Pacific Northwest Seismic Network (PNSN)

The recent events page on the  Pacific Northwest Seismic Network (PNSN)  can be very interesting, if you are following earthquake events in the Pacific Northwest. Here is a link to the page, and a sample graphic:


Pacific Northwest Seismic Network (PNSN) Recent Events webpage

Tsunami Evacuation Buildings (TEBs)

Tsunami Evacuation Buildings (TEBs) have been in widespread use in Japan for years. This January, Washington state began constructing the first TEB in the U.S. at Grays Harbor, WA. It will be a school as well as a vertical evacuation structure.


The nation's first tsunami vertical evacuation center breaks ground


This is an artist's rendering of the newly-constructed school and vertical evacuation center in Grays Harbor, Washington. 

This link to a HeraldNet article shows a picture of the building under construction on Oct. 8th, 2015


Link to HeraldNet article


A purpose-built TEB in Japan, along with the identification sign. As you can see, the Japanese are serious about this stuff. I'm sure we will be, too, hopefully before the next Full-Rip 9.0 earthquake on the Cascadia Subduction Zone.

The City of Cannon Beach, Oregon is serious about the risk of a tsunami from an earthquake on the Cascadia Subduction Zone. So, if you spend time on the coast (No. CA, OR, WA or B.C.) maybe you should be serious about it too. Here's a proposal for a Tsunami Evacuation Bldg (TEB) in Cannon Beach. The proposed structure would be a City Hall as well as a Tsunami Evacuation Building (TEB). 

Link to the City of Cannon Beach webpage

Useful YouTube Videos of Cascadia Subduction Zone Earthquakes & Tsunamis

Cascadia Subduction Zone Earthquake & Tsunami; 21 minutes

Published on Jan 9, 2014

Oregon Department of Geology & Mineral Industries

James Roddey explains the potential dangers of living near the Cascadia Subduction Zone. The Cascadia Subduction Zone can generate a magnitude 9 earthquake and devastating tsunami. Please note that James Roddey no longer works for the Oregon Geology Department.

James Roddey - Cascadia Earthquake Animation; 8:20 minutes

Published on Mar 30, 2012

http://www.readysetprepare.org - I adapted an animation originally created by he Pacific Northwest Seismic Network by adding text of what people would experience if "The Big One" hits the Pacific Northwest. I sometimes use this animation of a real-time magnitude 9.0 Cascadia Subduction Zone earthquake in my presentations.

The World's Most Dangerous Fault... Cascadia; 5:53 minutes

What are URMs?

URMs... URMs... what the heck are URMs? They're UnReinforced Masonry buildings, and Portland has 1800 of them, and that's from a survey conducted in the mid-1990s - 20 years ago. Remember this when you're enjoying that evening out in Old Town.

Unreinforced buildings could crumple in an earthquake