Categorized | Earthquake, Featured, News, Tsunami

Very strong 7.9M quake near Alaska, tsunami watch for Hawaii is CANCELLED


Hawaii County Civil Defense audio message at 1:15 a.m. Tuesday (Jan 23)

TSUNAMI MESSAGE NUMBER   3
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
110 AM HST TUE JAN 23 2018

TO - EMERGENCY MANAGEMENT IN THE STATE OF HAWAII

SUBJECT - TSUNAMI WATCH CANCELLATION

THE TSUNAMI WATCH IS CANCELLED FOR THE STATE OF HAWAII EFFECTIVE
AT 0110 AM HST.

AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS
NOTE REVISED EARTHQUAKE MAGNITUDE

   ORIGIN TIME - 1132 PM HST 22 JAN 2018
   COORDINATES - 56.0 NORTH  149.2 WEST
   LOCATION    - GULF OF ALASKA
   MAGNITUDE   - 7.9  MOMENT

MEASUREMENTS OR REPORTS OF TSUNAMI WAVE ACTIVITY

 GAUGE LOCATION        LAT   LON    TIME        AMPL         PER
 -------------------  ----- ------  -----  ---------------  -----
 DART 46403           52.6N 156.9W  1024Z   0.03M /  0.1FT  08MIN
 DART 46410           57.6N 143.8W  1008Z   0.04M /  0.1FT  06MIN
 DART 46409           55.3N 148.5W  0944Z   0.12M /  0.4FT  04MIN

 LAT  - LATITUDE (N-NORTH, S-SOUTH)
 LON  - LONGITUDE (E-EAST, W-WEST)
 TIME - TIME OF THE MEASUREMENT (Z IS UTC IS GREENWICH TIME)
 AMPL - TSUNAMI AMPLITUDE MEASURED RELATIVE TO NORMAL SEA LEVEL.
        IT IS ...NOT... CREST-TO-TROUGH WAVE HEIGHT.
        VALUES ARE GIVEN IN BOTH METERS(M) AND FEET(FT).
 PER  - PERIOD OF TIME IN MINUTES(MIN) FROM ONE WAVE TO THE NEXT.

 NOTE - DART MEASUREMENTS ARE FROM THE DEEP OCEAN AND THEY
        ARE GENERALLY MUCH SMALLER THAN WOULD BE COASTAL
         MEASUREMENTS AT SIMILAR LOCATIONS.

EVALUATION

 BASED ON ALL AVAILABLE DATA THERE IS NO TSUNAMI THREAT TO THE
 STATE OF HAWAII. THEREFORE... THE TSUNAMI WATCH FOR HAWAII IS NOW
 CANCELLED.

THIS WILL BE THE FINAL MESSAGE ISSUED FOR THIS EVENT UNLESS
ADDITIONAL DATA ARE RECEIVED.

Note that warnings/watches/advisories may continue for areas closer to the earthquake’s epicenter. View notices here: wcatwc.arh.noaa.gov

Projected tsunami travel times from the Alaska quake Monday, January 22, 2018.

Projected tsunami travel times from the Alaska quake Monday, January 22, 2018.

Preliminary tsunami surge modeling for severe earthquake near Alaska Monday, January 22, 2018.

Preliminary tsunami surge modeling for severe earthquake near Alaska Monday, January 22, 2018.

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.

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