West Coast Earthquakes (1 Viewer)

bjdeming

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Nothing major, just a swarm about 270 miles due west of me, on the ever-active submarine Blanco Fracture Zone. It's reportedly not related to the Cascadia subduction zone megathrust quake threat (about 40% chance in the next 50 years for that, experts report). No tsunami threat, either.

Just thought it might be handy to have a thread for this in case the Hayward or some other fault breaks loose.

I've been out here 7-1/2 years and only felt a fleeting little quiver from an active site northwest of Eugene (I was in Eugene then). It zoomed through so quickly no one realized what had happened! May all our quakes be so harmless and minor.
 
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TH2002

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There was a small earthquake (3.6 Mw) centered about 7 S Lytle Creek which is not far from where I live. Nothing huge obviously but of note is that it happened at about 2 in the morning and I woke up a few seconds before the (most intense?) shaking started.
 

bjdeming

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Oops:

Three loud sonic booms that shook buildings and people along the central Oregon coast Tuesday afternoon was caused by a mistake by an Oregon Air National Guard pilot during training exercises, a military spokesman said Wednesday.

Some authoritative person from the USGS, PNSN, or a university should take this opportunity for outreach and explain to the public the basic difference between a subduction zone (Cascadia):


And a transform fault (Blanco here; Mendocino and San Andreas offshore and in California, respectively):


Both are capable of intense damaging quakes, but they are two entirely different plate tectonics structures.

It would really cut down on public anxiety, if people understood this better.

The PNSN did note on their website (their emphasis):

The slip on these earthquakes are unlikely to have caused significant changes in stress along the Cascadia Subduction Zone 200 km closer to shore, which in the past has produced M9 earthquakes as recently as January 26, 1700.

Feeding off something mentioned in that second video, the Salton Sea area had a swarm earlier this year.
 
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bjdeming

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Speaking of the Mendocino fault zone...an M6.2:

The location and faulting mechanism indicate that the earthquake likely occurred on or near the east-west trending Mendocino fracture zone that demarks the plate boundary between the Pacific plate and southern Juan de Fuca plate (alternatively termed the Gorda plate).

The earthquake was located in the vicinity of the Mendocino triple junction – the region where the Pacific, North America, and Juan de Fuca plates meet.

The faulting mechanism of the December 20 earthquake is most consistent with the earthquake having occurred between the Juan de Fuca/Gorda and Pacific plates, as opposed to on the San Andreas fault (the boundary between the North America and Pacific plates) or on the Cascadia subduction zone interface (the boundary between the North America and Juan de Fuca plates)...

-- USGS


There was some damage but no deaths reported.

Aftershock forecast lists less than 1% chance of anything stronger here.

That Mendocino fault zone is really complex because it's also a triple junction. It might even shut down the Cascade volcanoes in the distant future (hopefully not before I get to see a small, pretty, nondamaging red-lava flow!).

Blanco is carrying on, too.

This is all just business as normal for transform faults, I think.
 

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