Mw 7.5 South of Alaskan Peninsula

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davenn
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Couldnt get to post this earlier in the day, work duties took precedence

A Mw 7.5 off shore south of Sand Point, Alaskan Peninsula some hours ago today
I will have to look through my records but I recall another similar sized event in the
same region within the last 10 -12 months


2020-10-19 20:54:40 (UTC) at 40 km deep and appears to be an oblique slip
rather than a pure strike slip event


It's still on my seismo for another ~ 15 hours
http://www.sydneystormcity.com/seismograms.htm

USGS report .....
https://earthquake.usgs.gov/earthquakes/eventpage/us6000c9hg/executive


cheers
Dave
 
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davenn
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Knew the other event wasn't so long ago

Mw 7.8 on the 22 July 2020
They are classifying today's Mw 7.5 an aftershock of the 7.8 .... just WOW

I have edited one of their maps to show both events
Today's event is about 80km SW of the July event

20200722 and 1019  Mw 7.8 and 7.5.JPG
 
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davenn
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It looks like there was no Tsunami warning caused by it? Is that because it was 40km deep?

EDIT -- It looks like there was indeed a Tsunami warning, but just for Alaska (not Northern California):
Yes, just a local warning which was cancelled within the hour

Yes, the depth played a part, as did the type of motion on the fault that ruptured. Tho the event was on a major subduction zone,
the fault that ruptured was primarily a strike/slip (sideways) motion rather than a thrust motion. As a result, the seafloor didn't
move with any significant vertical offset.


Dave
 
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davenn
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here's a screen dump of the seismogram from my system ......
201019 2054UT Mw7.5 S of Alaska Penin zhi1.gif
 

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