Register · Events
How tide gauges recorded the 2004 Indian Ocean tsunami
NOAA’s archive records a 1.94-metre maximum at the Colombo tide gauge and a first-arrival travel time of 2 hours 50 minutes. The Lamu record gives 0.50 metres and 8 hours 53 minutes. The figures describe measurements at particular gauges.
Sources checked
- Port Blair1.75 m
- Sibolga1.23 m
- Phuket1.11 m
- Hillarys Harbour0.55 m
- Colombo1.94 m
- Malé1.08 m
- Paradip1.59 m
- Salalah1.39 m
- Pointe La Rue1.39 m
- Lamu0.5 m
- Zanzibar0.36 m
- Richards Bay0.76 m
- Port Louis0.98 m
Natural Earth land outlines and dashed land boundaries.
Switch between the measured height and elapsed minutes. Each pin represents the archive’s gauge coordinates.
The archive records both a time and a height
The source event is the 26 December 2004 earthquake off Sumatra. The observations register records a time to first arrival and, where available, the maximum height measured at the gauge. Phuket’s record gives a travel time of 1 hour 56 minutes and a maximum of 1.11 metres. Source 2 Source 1 Source 4
The western observations document later arrivals
The Seychelles gauge at Pointe La Rue recorded a maximum of 1.39 metres and a travel time of 7 hours 17 minutes. Zanzibar recorded 0.36 metres and 9 hours 41 minutes. Those readings describe the selected instruments at their own locations. Source 1
Time to first arrival is separate from the largest wave
A first arrival marks when a signal first reached a gauge. NOAA has separate fields for when the maximum wave arrived. The elapsed times here use the first-arrival travel fields. They do not rank how quickly the largest signal arrived. Source 1 Source 4
A gauge reading differs from a field-survey runup
The NOAA and UNESCO summary separately describes survey crews measuring how high water reached on land. Its maximum runup estimate in Aceh was about 51 metres. That figure uses a different measurement method and is outside this gauge comparison. Source 3 Source 4