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M7.4 (prelim) south of Alaska (1 Viewer)


bjdeming

Member
2020 Supporter
Messages
290
Location
Corvallis, Oregon
Just got this email alert --haven't heard anything else yet. Emphasis added.



TSUNAMI MESSAGE NUMBER 1
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
2104 UTC MON OCT 19 2020

...PTWC TSUNAMI THREAT MESSAGE...


**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****

THIS MESSAGE IS ISSUED FOR INFORMATION ONLY IN SUPPORT OF THE
UNESCO/IOC PACIFIC TSUNAMI WARNING AND MITIGATION SYSTEM AND IS
MEANT FOR NATIONAL AUTHORITIES IN EACH COUNTRY OF THAT SYSTEM.

NATIONAL AUTHORITIES WILL DETERMINE THE APPROPRIATE LEVEL OF
ALERT FOR EACH COUNTRY AND MAY ISSUE ADDITIONAL OR MORE REFINED
INFORMATION.

**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****


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

* MAGNITUDE 7.4
* ORIGIN TIME 2055 UTC OCT 19 2020
* COORDINATES 54.7 NORTH 159.6 WEST
* DEPTH 41 KM / 25 MILES
* LOCATION SOUTH OF ALASKA


EVALUATION
----------

* AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 7.4 OCCURRED
SOUTH OF ALASKA AT 2055 UTC ON MONDAY OCTOBER 19 2020.

* BASED ON THE PRELIMINARY EARTHQUAKE PARAMETERS... HAZARDOUS
TSUNAMI WAVES ARE POSSIBLE FOR COASTS LOCATED WITHIN 300 KM
OF THE EARTHQUAKE EPICENTER.


TSUNAMI THREAT FORECAST
-----------------------

* HAZARDOUS TSUNAMI WAVES FROM THIS EARTHQUAKE ARE POSSIBLE
WITHIN 300 KM OF THE EPICENTER ALONG THE COASTS OF

NO AREAS COVERED BY THIS MESSAGE APPEAR TO BE IMMEDIATELY
THREATENED.
HOWEVER... THE SITUATION IS STILL UNDER
INVESTIGATION. THIS THREAT EVALUATION WILL BE UPDATED AS
SOON AS FURTHER INFORMATION BECOMES AVAILABLE.


RECOMMENDED ACTIONS
-------------------

* GOVERNMENT AGENCIES RESPONSIBLE FOR THREATENED COASTAL AREAS
SHOULD TAKE ACTION TO INFORM AND INSTRUCT ANY COASTAL
POPULATIONS AT RISK IN ACCORDANCE WITH THEIR OWN
EVALUATION... PROCEDURES AND THE LEVEL OF THREAT.

* PERSONS LOCATED IN THREATENED COASTAL AREAS SHOULD STAY ALERT
FOR INFORMATION AND FOLLOW INSTRUCTIONS FROM NATIONAL AND
LOCAL AUTHORITIES.


POTENTIAL IMPACTS
-----------------

* A TSUNAMI IS A SERIES OF WAVES. THE TIME BETWEEN WAVE CRESTS
CAN VARY FROM 5 MINUTES TO AN HOUR. THE HAZARD MAY PERSIST
FOR MANY HOURS OR LONGER AFTER THE INITIAL WAVE.

* IMPACTS CAN VARY SIGNIFICANTLY FROM ONE SECTION OF COAST TO
THE NEXT DUE TO LOCAL BATHYMETRY AND THE SHAPE AND ELEVATION
OF THE SHORELINE.

* IMPACTS CAN ALSO VARY DEPENDING UPON THE STATE OF THE TIDE AT
THE TIME OF THE MAXIMUM TSUNAMI WAVES.

* PERSONS CAUGHT IN THE WATER OF A TSUNAMI MAY DROWN... BE
CRUSHED BY DEBRIS IN THE WATER... OR BE SWEPT OUT TO SEA.


NEXT UPDATE AND ADDITIONAL INFORMATION
--------------------------------------

* THE NEXT MESSAGE WILL BE ISSUED IN ONE HOUR... OR SOONER IF
THE SITUATION WARRANTS.

* AUTHORITATIVE INFORMATION ABOUT THE EARTHQUAKE FROM THE U.S.
GEOLOGICAL SURVEY CAN BE FOUND ON THE INTERNET AT
EARTHQUAKE.USGS.GOV.

* FURTHER INFORMATION ABOUT THIS EVENT MAY BE FOUND AT
WWW.TSUNAMI.GOV.

* COASTAL REGIONS OF HAWAII... AMERICAN SAMOA... GUAM... AND
CNMI SHOULD REFER TO PACIFIC TSUNAMI WARNING CENTER MESSAGES
SPECIFICALLY FOR THOSE PLACES THAT CAN BE FOUND AT
WWW.TSUNAMI.GOV.

* COASTAL REGIONS OF CALIFORNIA... OREGON... WASHINGTON...
BRITISH COLUMBIA AND ALASKA SHOULD ONLY REFER TO U.S.
NATIONAL TSUNAMI WARNING CENTER MESSAGES THAT CAN BE FOUND
AT WWW.TSUNAMI.GOV.

$$

DISCLAIMER :The regional tsunami forecast information provided does not originate within IOC-UNESCO. IOC-UNESCO is transmitting this information on an unofficial basis. Tsunami Services Providers officially provide this information to the designated Tsunami Warning Focal Points / National Tsunami Warning Centres (TWFP/NTWC) of Member States. It is then, the responsibility of mandated national organisations operating within the legal framework of the sovereign nation in which they reside and serve, to provide alerts to their citizens and communities. UNESCO does not warrant, guarantee, or make any representations regarding the timeliness, currency, correctness, accuracy, reliability, or other aspect of the characteristics or use of the information. To unsubscribe from this list please visit
https://lists.unesco.org/wws/sigrequest/tsunami-information-ioc
 

bjdeming

Member
2020 Supporter
Messages
290
Location
Corvallis, Oregon
This is officially considered an aftershock of the big one earlier this year, and here's the updated aftershock forecast per https://earthquake.usgs.gov/earthquakes/eventpage/us7000asvb/oaf/commentary :

Our detailed aftershock forecast​

The USGS estimates the chance of more aftershocks as follows: Within the next 1 Month until 2020-11-19 00:00:00 (UTC):

  • The chance of an earthquake of magnitude 3 or higher is > 99 %, and it is most likely that as few as 21 or as many as 53 such earthquakes mayoccur in the case that the sequence is re-invigorated by a larger aftershock.
  • The chance of an earthquake of magnitude 5 or higher is 30 %, and it is most likely that as few as 0 or as many as 3 such earthquakes mayoccur.
  • The chance of an earthquake of magnitude 6 or higher is 3 %, such an earthquake is possible but with a low probability.
  • The chance of an earthquake of magnitude 7 or higher is 1 in 300,such an earthquake is possible but with a low probability.
 

bjdeming

Member
2020 Supporter
Messages
290
Location
Corvallis, Oregon
Updated aftershock forecast. In other notes read, this appears to have been an unusual event, but the details are over my head:

Our detailed aftershock forecast​

The USGS estimates the chance of more aftershocks as follows: Within the next 1 Month until 2020-11-20 07:00:00 (UTC):

  • The chance of an earthquake of magnitude 3 or higher is > 99 %, and it is most likely that as few as 59 or as many as 110 such earthquakes mayoccur in the case that the sequence is re-invigorated by a larger aftershock.
  • The chance of an earthquake of magnitude 5 or higher is 56 %, and it is most likely that as few as 0 or as many as 4 such earthquakes mayoccur.
  • The chance of an earthquake of magnitude 6 or higher is 8 %, and it is most likely that as few as 0 or as many as 2 such earthquakes mayoccur.
  • The chance of an earthquake of magnitude 7 or higher is 1 in 100,such an earthquake is possible but with a low probability.
 

Lori

Administrator
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Administrator
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Pelham, AL
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I had no idea that aftershocks could be months later and so strong!!
 
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