Mw 7.5 South of Alaskan Peninsula

[davenn]

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 months2020-10-19 20:54:40 (UTC) at 40 km deep and appears to be an oblique slip
rather than a pure strike slip eventIt's still on my seismo for another ~ 15 hours
http://www.sydneystormcity.com/seismograms.htm

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

 

[davenn]

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

 

[berkeman]

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):

https://abc7news.com/weather/alaska-earthquake-measuring-75-triggers-tsunami-warning/7166453/

 

[davenn]

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 canceled 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

 

[DaveE]

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):

https://abc7news.com/weather/alaska-earthquake-measuring-75-triggers-tsunami-warning/7166453/

And Hawaii closed some beaches. I guess that's like 1/2 a warning? They saw 1 ft waves, IIRC.

 

[davenn]

here's a screen dump of the seismogram from my system ...