National 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 National Tsunami Warning Center (NTWC). 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 NTWC 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