2021 has been a hell of a year.
And for the state of Oregon, it is concluding with a spectacular display of geology.
Dozens of earthquakes rattled off the coast of Oregon over the past 24 hours — some reaching 5.8-magnitude — but none caused major damage or tsunamis.About 60 temblors shook in the Blanco Transform Fault Zone about 200 miles off the shore, U.S. Geological Survey data indicates. The quakes were centered roughly due west of Newport, beginning Tuesday morning and occurring into Wednesday, The Oregonian reported.At least eight of the earthquakes were 5.5-magnitude or higher, the strength that would typically cause damage if closer to land.
The reason for the concern that was evident in social media is the fault is close to the infamous Cascadia Subduction Zone. This region is noted for its periodic, massive earthquakes and resultant tsunami.
The last earthquake that occurred in this fault was on January 26, 1700, with an estimated 9.0 magnitude. This earthquake caused the coastline to drop several feet and a tsunami to form and crash into the land.What is most surprising is that evidence for this great earthquake also came from Japan. Japanese historic records indicate that a destructive distantly-produced tsunami struck their coast on January 26, 1700. By studying the geological records and the flow of the Pacific Ocean, scientists have been able to link the tsunami in Japan with the great earthquake from the Pacific Northwest. Native American legends also support to the timing of this last event.
More on the Cascadia Subduction Zone can be found here.
The good news is that the fault line where the swarm is occurring is a different type of fault system. The ensuing quakes should not cause major structural damage or tsunamis.
“The Blanco Fracture Zone is not connected directly to the subduction zone so it won’t affect the big fault under land (Cascadia megathrust),” said Eric J. Fielding, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.”M5s on Blanco are very common and have never been followed by something on land. Plate tectonics in real time,” said seismologist Lucy Jones, referring to magnitude 5 temblors in the area.The Blanco Fault Zone is a transform, or strike-slip, boundary; that means it’s where tectonic plates slide along one another. The most dangerous and powerful faults are usually seen in subduction zones, where one plate dives beneath another.
To put it into parlance that we can all now understand: Cascadia is the Delta variant, and Blanco is the Omicron variant.
Better yet: Blanco earthquakes are fun and not fearsome.
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