Categorized | Earthquake, News, Tsunami

Severe 8.6M earthquake strikes off the coast of Sumatra, no tsunami threat to Hawaii

Magnitude
8.6
Date-Time
Wednesday, April 11, 2012 at 08:38:37 UTC
Wednesday, April 11, 2012 at 02:38:37 PM at epicenter
Tuesday, April 10, 2012 at 10:38:38 PM (HST) – Hawaii Standard (Honolulu)
Location
2.311°N, 93.063°E
Depth
22.9 km (14.2 miles)
Region
OFF THE WEST COAST OF NORTHERN SUMATRA
Distances
434 km (269 miles) SW of Banda Aceh, Sumatra, Indonesia
550 km (341 miles) SW of Lhokseumawe, Sumatra, Indonesia
963 km (598 miles) W of KUALA LUMPUR, Malaysia
1797 km (1116 miles) WNW of JAKARTA, Java, Indonesia

TSUNAMI BULLETIN NUMBER 007
PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS
ISSUED AT 1318Z 11 APR 2012

THIS BULLETIN IS FOR ALL AREAS OF THE INDIAN OCEAN.

… TSUNAMI WATCH CANCELLATION SUPPLEMENT …

… UPDATED SEA-LEVEL MEASUREMENTS …

THIS BULLETIN IS ISSUED AS ADVICE TO GOVERNMENT AGENCIES. ONLY NATIONAL AND LOCAL GOVERNMENT AGENCIES HAVE THE AUTHORITY TO MAKE DECISIONS REGARDING THE OFFICIAL STATE OF ALERT IN THEIR AREA AND ANY ACTIONS TO BE TAKEN IN RESPONSE.

AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS

ORIGIN TIME – 0839Z 11 APR 2012
COORDINATES – 2.3 NORTH 93.1 EAST
LOCATION – OFF W COAST OF NORTHERN SUMATRA
MAGNITUDE – 8.7

Current time in UTC/GMT/Z

MEASUREMENTS OR REPORTS OF TSUNAMI WAVE ACTIVITY

 GAUGE LOCATION        LAT   LON    TIME        AMPL         PER
 -------------------  ----- ------  -----  ---------------  -----
 MALE MV               4.2N  73.5E  1223Z   0.19M /  0.6FT  06MIN
 GAN MV                0.7S  73.2E  1212Z   0.03M /  0.1FT  48MIN
 HANIMAADHOO MV        6.8N  73.2E  1235Z   0.25M /  0.8FT  06MIN
 PADANG ID             1.0S 100.4E  1208Z   0.09M /  0.3FT  34MIN
 KO TAPHAO NOI TH      7.8N  98.4E  1143Z   0.05M /  0.2FT  06MIN
 ENGGANO ID            5.3S 102.3E  1104Z   0.12M /  0.4FT  04MIN
 TRINCONMALEE LK       8.6N  81.2E  1129Z   0.06M /  0.2FT  16MIN
 TELUKDALAM ID         0.6N  97.8E  1044Z   0.22M /  0.7FT  14MIN
 COCOS ISLAND AU      12.1S  96.9E  1102Z   0.08M /  0.3FT  18MIN
 SABANG ID             5.8N  95.3E  1010Z   0.36M /  1.2FT  06MIN
 MEULABOH ID           4.1N  96.1E  1007Z   1.06M /  3.5FT  12MIN
 DART 23401            8.9N  88.5E  0956Z   0.03M /  0.1FT  06MIN

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

A SIGNIFICANT TSUNAMI WAS GENERATED BY THIS EARTHQUAKE. HOWEVER…SEA LEVEL READINGS NOW INDICATE THAT THE THREAT HAS DIMINISHED OR IS OVER FOR MOST AREAS. THEREFORE THE TSUNAMI WATCH ISSUED BY THIS CENTER IS NOW CANCELLED.

FOR ANY AFFECTED AREAS – WHEN NO MAJOR WAVES HAVE OCCURRED FOR AT LEAST TWO HOURS AFTER THE ESTIMATED ARRIVAL TIME OR DAMAGING WAVES HAVE NOT OCCURRED FOR AT LEAST TWO HOURS THEN LOCAL AUTHORITIES CAN ASSUME THE THREAT IS PASSED. DANGER TO BOATS AND COASTAL STRUCTURES CAN CONTINUE FOR SEVERAL HOURS DUE TO RAPID CURRENTS. AS LOCAL CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE ALL CLEAR DETERMINATION MUST BE MADE BY LOCAL AUTHORITIES.

THIS WILL BE THE FINAL BULLETIN ISSUED BY THE PACIFIC TSUNAMI WARNING CENTER FOR THIS EVENT UNLESS ADDITIONAL INFORMATION BECOMES AVAILABLE.

THE JAPAN METEOROLOGICAL AGENCY MAY ISSUE ADDITIONAL INFORMATION FOR THIS EVENT. IN THE CASE OF CONFLICTING INFORMATION…THE MORE CONSERVATIVE INFORMATION SHOULD BE USED FOR SAFETY.

Projected travel times for a tsunami in the Indian Ocean.

Projected travel times for a tsunami in the Indian Ocean.

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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