Historical tsunamis · Sep 8, 1948, 3:09 PM UTC
1948 Tonga Trench tsunami
Tonga
The tsunami of Sep 8, 1948, 3:09 PM UTC originated near Tonga Trench (Tonga).
Key facts
- Date
- Sep 8, 1948, 3:09 PM UTC
- Cause
- Earthquake
- Magnitude
- M7.8
- Depth
- 33 km
- Maximum documented water height
- 0.10 m
- Observation records
- 7
- Countries affected
- 4
It was triggered by a magnitude 7.8 earthquake at a depth of 33 km.
The highest documented water height was 0.10 m (Hilo, Hawaii, Hi, United States).
7 observation sites in 4 countries are recorded.
Outside the source country, the earliest documented arrival was at Honolulu, Oahu, Hi (United States) after 6:36 h.
Map of observation sites
7Each dot is a documented observation site; colour and size show the observed water height. The triangle marks the source.
Tsunami arrival times
Documented arrival times from the NOAA/NCEI database, showing the earliest recorded location per country. Coverage is incomplete: a country without an entry was not necessarily spared.
- 0:00 hEarthquake (origin) · Sep 8, 1948, 3:09 PM UTC
- 6:36 hUnited States · Honolulu, Oahu, Hi · 0.10 m
2 places with a documented arrival time
Observations by country
| Country | Observation records | Maximum documented water height | Deaths | Earliest arrival |
|---|---|---|---|---|
 United States | 4 | 0.10 m Hilo, Hawaii, Hi | — | 6:36 h |
| USA Territory | 1 | 0.10 m Pago Pago, American Samoa | — | — |
 Australia | 1 | — | — | — |
 Cook Islands | 1 | — | — | — |
Highest documented water heights
7 / 7Individual documented observations for this event. Heights come from different measurement types and sources; not every location has a measured height.
| Location / station | Observed height | Distance from source | Country |
|---|---|---|---|
| Hilo, Hawaii, Hi · Hi | 0.10 m | 4,956 km | United States |
| Honolulu, Oahu, Hi · Hi | 0.10 m | 4,998 km | United States |
| Pago Pago, American Samoa · As | 0.10 m | 823 km | USA Territory |
| Port Allen, Kauai, Hi · Hi | 0.10 m | 4,999 km | United States |
| Waianae, Oahu, Hi · Hi | 0.10 m | 5,000 km | United States |
| Fort Denison, Sydney Harbor | — | 3,698 km | Australia |
| Rarotonga | — | 1,480 km | Cook Islands |
More tsunamis
Source: NOAA National Centers for Environmental Information (NCEI), Global Historical Tsunami Database. Confirmed events only. Deaths and damage are database estimates; older records are incomplete. Water heights come from different types of observation.