Clark County Today takes a look back at the likelihood of a major rip of the full Cascadia Subduction Zone that would trigger a magnitude 9.0 earthquake in the next 50 years
John Ley
for Clark County Today
The Great ShakeOut earthquake drill will take place on Thursday (Oct. 17) at 10:17 a.m. This is the time when the first shake is simulated, and participants should drop, cover, and hold on for at least 60 seconds. But locally, what are the odds of a major earthquake?
“Oregon is pretty boring,” says Harold Tobin, director of the PNW Seismic Network. He shared a video highlighting 40 years of earthquakes at the 2019 Pacific Northwest Earthquake Forum. Tobin noted most of the earthquakes have been in California, Washington, or offshore.
The biggest concern is a major rip of the full Cascadia Subduction Zone triggering a magnitude 9.0 earthquake in the range of 10-14 percent in the next 50 years. Put another way, there is an 86 to 90 percent chance an M9 earthquake will NOT happen in the next 50 years.
This is also relevant in the current Interstate Bridge Replacement Program (IBR) discussion for replacing the current two bridge structures. People should know the IRB is NOT designing the replacement bridge to the highest standard, which would best withstand an M9 or greater earthquake. They have previously reported they are not designing it to the 2,500-year standard; but a 500-year standard, which is the most commonly used standard for assessing seismic risk.
Read the following article Clark County Today published three years ago, regarding earthquakes here in the Pacific Northwest, as part of this year’s “Great Shakeout” event.
An additional article is about Oregon’s plans addressing seismic vulnerabilities to their transportation system.
Also read:
- POLL: Should the I-5 Bridge project be paused over cost and bidding concerns?
Clark County Today’s weekly poll asks whether the I-5 Bridge replacement should be paused as questions grow around rising costs and a lack of competitive bids. - Opinion: TriMet contract: MAX vehicles cost $4.5 millionRep. John Ley examines TriMet’s MAX vehicle purchases, arguing most were replacements and not connected to the bridge project.
- Expect delays on I-5 near Woodland for bridge inspection, May 18WSDOT will close a lane of southbound I-5 near Woodland on May 18 for a safety inspection.
- Opinion: ‘I’m more than just a little skeptical that IBR officials are doing everything they can to limit the cost of this project’
Ken Vance shares his concerns over rising costs and limited contractor interest in the Interstate Bridge Replacement Program. - Letter: ‘IBR has relied on this video to instill fear in the public and government officials to promote the construction of a new bridge’Bob Ortblad questions IBR’s use of a seismic video and urges a shift toward tunnel alternatives in this critical letter to the editor.
