M7.8 in Aleutians

[bjdeming]

It was shallow but offshore and the USGS PAGER code is green.

Per Tsunami.gov right now:

PRELIMINARY EARTHQUAKE PARAMETERS
---------------------------------

* MAGNITUDE 7.8
* ORIGIN TIME 0613 UTC JUL 22 2020
* COORDINATES 55.2 NORTH 158.6 WEST
* DEPTH 13 KM / 8 MILES
* LOCATION ALASKA PENINSULA


EVALUATION
----------

* AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 7.8 OCCURRED IN
THE ALASKA PENINSULA AT 0613 UTC ON WEDNESDAY JULY 22 2020.

* BASED ON ALL AVAILABLE DATA... HAZARDOUS TSUNAMI WAVES ARE
NOT FORECAST FOR SOME COASTS.
WE ARE STILL WAITING FOR MORE DATA TO CONFIRM.


TSUNAMI THREAT FORECAST...UPDATED
---------------------------------

* TSUNAMI WAVES ARE FORECAST TO BE LESS THAN 0.3 METERS ABOVE
THE TIDE LEVEL FOR THE COASTS OF

CHUUK... GUAM... HAWAII... HOWLAND AND BAKER... JAPAN...
JOHNSTON ATOLL... KIRIBATI... KOSRAE... MARSHALL
ISLANDS... MEXICO... MIDWAY ISLAND... NORTHERN MARIANAS...
NORTHWESTERN HAWAIIAN ISLANDS... PALAU... PALMYRA
ISLAND... POHNPEI... RUSSIA... WAKE ISLAND... AND YAP.

However, a seismologist I follow just tweeted



and then commented that the signals are smaller at other buoys. Hope it's just local conditions.

No warnings at the PNW coasts yet .

Here's an updating Alaska news source: https://www.alaskapublic.org/2020/0...i-warning-for-sand-point-cold-bay-and-kodiak/

And the Sand Point data graphic: https://tidesandcurrents.noaa.gov/tsunami/plot.html?stnid=9459450&name=Sand Point&refresh=1

 

[bjdeming]

PTWC says the threat is over: just half-foot wave at Sand Point. Whew! Now to just watch the USGS aftershock forecasts and hope this wasn't a foreshock.

Those NOAA data graphics are great, BTW.

 

[bjdeming]

M6.1 just now -- the largest aftershock thus far. No tsunami risk.

It's worth mentioning because the most recent USGS aftershock forecast at https://earthquake.usgs.gov/earthquakes/eventpage/us7000asvb/oaf/commentary gave a low probability to M6 or higher, but did note that it could happen.

Chances for an M7 or higher are even less: 1 in 300. But they can't rule it out.