Categorized | Earthquake, News

Very strong 7.8M quake off-shore Japan, no tsunami threat Saturday (May 30)

Magnitude
7.8

Time
2015-05-30 11:23:02 (UTC)
2015-05-30 01:23:02 HST

Nearby Cities
189km (117mi) WNW of Chichi-shima, Japan
771km (479mi) SSE of Shimoda, Japan
781km (485mi) SSE of Oyama, Japan
783km (487mi) SE of Shingu, Japan
874km (543mi) S of Tokyo, Japan

TSUNAMI INFORMATION STATEMENT NUMBER 1
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
1133 UTC SAT MAY 30 2015

...PTWC TSUNAMI INFORMATION STATEMENT...

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

  * MAGNITUDE      8.5
  * ORIGIN TIME    1123 UTC MAY 30 2015
  * COORDINATES    27.9 NORTH  140.8 EAST
  * DEPTH          696 KM / 432 MILES
  * LOCATION       BONIN ISLANDS  JAPAN REGION


EVALUATION
----------

  * AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 8.5 OCCURRED IN
    THE BONIN ISLANDS, JAPAN REGION AT 1123 UTC ON SATURDAY MAY 30
    2015.

  * BASED ON ALL AVAILABLE DATA... THERE IS NO TSUNAMI THREAT
    BECAUSE THE EARTHQUAKE IS LOCATED TOO DEEP INSIDE THE EARTH.


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

  * NO ACTION IS REQUIRED.


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

  * THIS WILL BE THE ONLY STATEMENT ISSUED FOR THIS EVENT UNLESS
    ADDITIONAL DATA ARE RECEIVED OR THE SITUATION CHANGES.

  * AUTHORITATIVE INFORMATION ABOUT THE EARTHQUAKE FROM THE U.S.
    GEOLOGICAL SURVEY CAN BE FOUND ON THE INTERNET AT
    EARTHQUAKE.USGS.GOV/EARTHQUAKES -ALL LOWER CASE-.

  * FURTHER INFORMATION ABOUT THIS EVENT MAY BE FOUND AT
    PTWC.WEATHER.GOV AND 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
    PTWC.WEATHER.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
    NTWC.ARH.NOAA.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.

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