Categorized | Earthquake, News

Very large 7.9M earthquake near Alaska, tsunami advisory for Alaska is cancelled, none for Hawaii


View M7.9 – 24km SE of Little Sitkin Island, Alaska – 2014-06-23 20:53:09 UTC in a larger map

Magnitude
M7.9 (revised by USGS)

Event Time
2014-06-23 20:53:09 UTC
2014-06-23 11:53:09 UTC-09:00 at epicenter
2014-06-23 10:53:09 UTC-10:00 system time

Location
51.797°N 178.760°E depth=107.5km (66.8mi)

Nearby Cities
24km (15mi) SE of Little Sitkin Island, Alaska
1370km (851mi) E of Petropavlovsk-Kamchatskiy, Russia
1387km (862mi) E of Vilyuchinsk, Russia
1388km (862mi) E of Yelizovo, Russia
2957km (1837mi) W of Whitehorse, Canada

UPDATED (2:48 PM on 6/23/2014)

PUBLIC TSUNAMI MESSAGE NUMBER 6
NWS NATIONAL TSUNAMI WARNING CENTER PALMER AK
435 PM AKDT MON JUN 23 2014

...THE TSUNAMI ADVISORY IS CANCELLED...


CANCELLATIONS
-------------
* THE TSUNAMI ADVISORY IS CANCELED FOR THE COASTAL AREAS OF
  ALASKA FROM NIKOLSKI ALASKA TO ATTU ALASKA


IMPACTS - UPDATED
-----------------
* A TSUNAMI WAS GENERATED DURING THIS EVENT BUT NO LONGER
  POSES A THREAT.

* SOME AREAS MAY CONTINUE TO SEE SMALL SEA LEVEL CHANGES.

* THE DETERMINATION TO RE-OCCUPY HAZARD ZONES MUST BE MADE BY
  LOCAL OFFICIALS.


RECOMMENDED ACTIONS - UPDATED
-----------------------------
* DO NOT RE-OCCUPY HAZARD ZONES UNTIL LOCAL EMERGENCY OFFICIALS
  INDICATE IT IS SAFE TO DO SO.


OBSERVATIONS OF TSUNAMI ACTIVITY - UPDATED
------------------------------------------
                                 TIME             OBSERVED MAX
SITE                         OF MEASUREMENT       TSUNAMI HEIGHT
---------------------------- ---------------      --------------
AMCHITKA  AK                 2322 UTC  06-23        00.7FT
SHEMYA  AK                   2305 UTC  06-23        00.2FT
ADAK  AK                     2302 UTC  06-23        00.2FT
NIKOLSKI  AK                 2323 UTC  06-23        00.2FT
ST PAUL IS.  AK              2329 UTC  06-23        00.2FT
DUTCH HARBOR  AK             2330 UTC  06-23        00.3FT
ATKA  AK                     2350 UTC  06-23        00.6FT

HEIGHT - OBSERVED MAX TSUNAMI HEIGHT IS THE WATER LEVEL ABOVE THE
         TIDE LEVEL AT THE TIME OF MEASUREMENT.


NEXT UPDATE AND ADDITIONAL INFORMATION
--------------------------------------
* THIS WILL BE THE FINAL U.S. NATIONAL TSUNAMI WARNING CENTER
  MESSAGE ISSUED FOR THIS EVENT.

* REFER TO THE INTERNET SITE NTWC.ARH.NOAA.GOV FOR MORE
  INFORMATION.

* PACIFIC COASTAL REGIONS OUTSIDE CALIFORNIA... OREGON...
  WASHINGTON... BRITISH COLUMBIA AND ALASKA SHOULD REFER TO THE
  PACIFIC TSUNAMI WARNING CENTER MESSAGES AT PTWC.WEATHER.GOV.

USGS: How large does an earthquake have to be to cause a tsunami?

Magnitudes below 6.5
Earthquakes of this magnitude are very unlikely to trigger a tsunami.

Magnitudes between 6.5 and 7.5
Earthquakes of this size do not usually produce destructive tsunamis. However, small sea level changes may be observed in the vicinity of the epicenter. Tsunamis capable of producing damage or casualties are rare in this magnitude range but have occurred due to secondary effects such as landslides or submarine slumps.

Magnitudes between 7.6 and 7.8
Earthquakes of this size may produce destructive tsunamis especially near the epicenter; at greater distances small sea level changes may be observed. Tsunamis capable of producing damage at great distances are rare in the magnitude range.

Magnitude 7.9 and greater
Destructive local tsunamis are possible near the epicenter, and significant sea level changes and damage may occur in a broader region.

Note that with a magnitude 9.0 earthquake, the probability of an aftershock with a magnitude exceeding 7.5 is not negligible. To date, the largest aftershock recorded has been magnitude 7.1 that did not produce a damaging tsunami.

20140623_tsunami-alaska-traveltime

20140623-quake-alaska-energymap

Energy Map of the earthquake

Sea level monitoring station at Adak, Alaska measured a wave height of 0.2 feet.

Sea level monitoring station at Adak, Alaska measured a wave height of 0.2 feet.

Sea level monitoring station at Atak, Alaska.

Sea level monitoring station at Atak, Alaska.

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