West Coast/Alaska Tsunami Warning Center, NOAA/NWS

TSUNAMI of 11 April, 2012 (Off the West Coast of Northern Sumatra)

A great earthquake with a moment magnitude of 8.6 (USGS magnitude) occurred at 08:38:37 UTC 11 April 2012 (day 102) and was located 270 mi/433 km SW of Banda Aceh, Sumatra, Indonesia (2.311N, 93.063E, 14.2 mi/22.8 km depth--USGS location).

A second quake followed 2hrs and 5 minutes later. This aftershock had a moment magnitude of 8.2 (USGS magnitude) and occurred at 10:43:09 UTC. It was located 382 mi/613 km SSW of Banda Aceh, Sumatra, Indonesia (0.773N, 92.452E, 10.2 mi/16.4 km depth--USGS location).

Both earthquakes produced a tsunami that was recorded at tide gages monitored by the West Coast/Alaska Tsunami Warning Center (WCATWC). Many observatories provide data to the centers; such as the NOAA National Ocean Service, the U. of Hawaii Sea Level Center, the Chilean Navy, the Japan Meteorological Agency and the National Tidal Facility in Australia among others. Click on the site name to see a graph of the tsunami, when available. Listed wave heights are maximum amplitude in cm (above sea level). Observed Arrival time is the actual tsunami arrival time in UTC on gages where it could be determined. The Computed Arrival time is the estimated time of wave arrival computed at the WCATWC based on the earthquake origin time and location. The Sample Interval column shows the time between data samples.

For additional information about this tsunami event see the Pacific Tsunami Warning Center's homepage.


Travel Time Map (click to enlarge)	Maximum Amplitude Graph (PTWC rift model) (click to enlarge)

Tide gage/ Measurement Location	Estimated Arrival Time [UTC (J.Day)]	Observed Arrival time [UTC (J.Day)]	Peak amplitude (above sea level in cm)	Time of Peak Amplitude Measurement [UTC (J.Day)]	Model Forecast Amplitude (above sea level in cm)	Initial motion	Sample Interval (min)	Data File (Julian Day Starts at 0000 UTC)
Sabang, Indonesia	0939 (102)	0943 (102)	40	1009 (102)	-	up	1	102, 103
Meulaboh, Indonesia	-	0959 (102)	107	1031 (102)	-	up	1	102, 103
Talukdalam, Indonesia	-	0946 (102)	31	1213 (102)	-	up	1	102, 103
Hillary Harbor, Australia	1453 (102)	1458 (102)	8	0226 (103)	-	down	1	102, 103
Cocos Islands, Australia	1035 (102)	1043 (102)	7	1102 (102)	-	down	1	102, 103
Enggano, Indonesia	-	1033 (102)	13	1253 (102)	-	down	1	102, 103
Trinconmalee, Sri_Lanka	1038 (102)	1115 (102)	9	1125 (102)	-	up	1	102, 103
Ko Taphao, Thailand	1128 (102)	1132 (102)	11	1402 (102)	-	down	1	102, 103
Hanimaadhoo, Maldives	1203 (102)	1210 (102)	4	1404 (102)	-	down	1	102, 103
Rodrigues, Mauritus	1403 (102)	1351 (102)	20	1444 (102)	-	up	1	102, 103
Prigi, Indonesia	-	1431 (102)	9	1800 (102)	-	down	1	102, 103
Gan, Maldives	1147 (102)	1119 (102)	3	1235 (102)	-	up	1	102, 103
Port Louis, Mauritus	1456 (102)	1454 (102)	17	1605 (102)	-	down	1	102, 103
Pointe La Rue, Seychelles	1528 (102)	1544 (102)	12	0024 (103)	-	down	1	102, 103
Pointe des Galets, Reunion Is.	-	1537 (102)	6	1805 (102)	-	down	1	102, 103
Sainte Marie, Reunion Is.	-	1439 (102)	20	0507 (103)	-	up	1	102, 103

The following section gives arrival times based on the second earthquake. Due to the time between the two quakes and the constructive/destructive interference between the two tsunamis, definitive times and amplitudes due to the second quake cannot be discerned.

Tide gage/ Measurement Location	Estimated Arrival Time [UTC (J.Day)]	Observed Arrival time [UTC (J.Day)]	Peak amplitude (above sea level in cm)	Time of Peak Amplitude Measurement [UTC (J.Day)]	Model Forecast Amplitude (above sea level in cm)	Initial motion	Sample Interval (min)	Data File (Julian Day Starts at 0000 UTC)
Sabang, Indonesia	1204 (102)	?	?	?	-	?	1	102, 103
Dart 23401	1205 (102)	1213	4	1219 (102)	-	?	15 SEC	--
Cocos Islands, Australia	1234 (102)	?	?	?	-	?	1	102, 103
Trinconmalee, Sri_Lanka	1249 (102)	?	?	?	-	?	1	102, 103
Gan, Maldives	1341 (102)	?	?	?	-	?	1	102, 103
Hanimaadhoo, Maldives	1406 (102)	?	?	?	-	?	1	102, 103
Rodrigues, Mauritus	1557 (102)	?	?	?	-	?	1	102, 103
Port Louis, Mauritus	1650 (102)	?	?	?	-	?	1	102, 103
Pointe La Rue, Seychelles	1722 (102)	?	?	?	-	?	1	102, 103


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