A M4.5 quake between Port Orford and Coos Bay, Oregon has scientists very interested because it has a connection to the big Cascadia earthquake forecast for our future.
The Pacific Northwest is rumbling. You just might not know it.
A 9.0 Cascadia Subduction Zone earthquake strikes the Northwest. Picture via NOAA Simulation
On Sunday at 12:31 p.m., a M3.4 earthquake rattled south of Mount Rainier, jolting a seismic region near Goat Rocks, which produced a damaging 5.5 earthquake back in 1981.
Three minutes later, a M4.1 quake struck off the coast Washington’s most northwest corner and is most probably connected with offshore plate movement.
Those Weren’t The Only Quakes
A list of the recent earthquakes can be found here.
The earthquake getting the most attention from scientists struck around 5:45 p.m. on Friday, Nov. 29.
The quake is intriguing for its magnitude and location. It registered at M4.5 and struck southwest of Coos Bay in Port Orford, which is near the Oregon coast and the Cascadia Subduction Zone.
The 4.5 quake was strong enough to set off the new ShakeAlert earthquake early warning system, telling people as far away as Grants Pass that shaking might be coming.
Scientists can’t pinpoint exactly where the quake happened under Port Orford. It could have been in the diving ocean plate itself, it could have been in the continental plate which is also under pressure, or if it’s on the actual Cascadia fault itself, that raises even more questions.
Earthquakes Are Rare in Cascadia Subduction Zone
According to PNSN scientists, earthquakes are rare in the subduction zone. So when they see an earthquake that might be in that subduction zone interface, that does get their attention!
The Northwest doesn’t have as many earthquakes in the Cascadia Subduction Zone compared to other subduction zones around the world, most of which are on the Pacific Rim.
Geologic Settings of Washington and Oregon
The Pacific Northwest Seismic Network (PNSN) tracks earthquakes in both Washington and Oregon.
The two states also fall along a 600-plus mile fault zone running offshore known as the Cascadia Subduction Zone.
The subduction zone is where part of the ocean floor known as the Juan de Fuca plate is being forced underneath the North American crustal plate.
The two plates are considered locked together and when the compressive tectonic pressure becomes too great, they are expected to slide past each other and cause up to a 9.2 magnitude quake.
All these quakes are interconnected somehow and are a fresh reminder of how seismically-active the Pacific Northwest is and will remain. [King5]