May 11, 1981 Tsunami: Agulhas Bank, South Africa
A tsunami caused by a landslide began at Agulhas Bank, South Africa on May 11, 1981 at 07:10 UTC. The water rose as high as 0.29 meters. Its effects were recorded at 9 places in at least 2 countries.
Where the waves reached
The source (white) and every runup with a place, colored by the water height recorded there. A ring is a runup NCEI marks doubtful.
- Under 1 m
- 1 to 3 m
- 3 to 10 m
- 10 to 30 m
- 30 m and more
- Height not recorded
The tsunami
- Date
- May 11, 1981, 07:10 UTC
- Source
- Agulhas Bank, South Africa
- Cause
- Landslide
- Maximum water height
- 0.29 m (1.0 ft)
- Runups recorded
- 9
- Waters
- Ocean
- How certain
- Questionable tsunami
- Source location
- 35.616° S, 20.267° E
The toll
The record gives no deaths, injuries or damage for this tsunami.
What the record says
NCEI’s account, from the sources it cites.
On May 11, 1981, tide stations on the coast of South Africa
registered unusual tsunami-1ike waves. Analogue records from Saldanha Bay to East London, 1000 km eastward along the
coast, and at intermediate tidal stations. Largest maximum wave was registered at Mosselbaai with a trough-to-crest height of 58 cm after removal of tide. Source of these tsunami-like waves has not been absolutely determined. No earthquake approaching tsunamigenic potential preceded the
arrival of the waves. Atmospheric conditions were not abnormal, nor were the characteristics of the initial waves indicative of a meteorological origin. Submarine landslide may have initiated the disturbance, and this possibility
is investigated. The source position has been estimated by inverse calculations of wave velocities from the observed arrival times at coastal positions. It appears to have originated on Agulhas Bank, 90 km southward of Cape Agulhas, in a charted depth of 140 m.
The event was registered on tide gauges in Simonstown, Mosselbaai, Knysna and Port Elizabeth. (reference #484)
Every runup
Nearest the source first. Heights are above sea level at the time; a tide gauge reads half the wave’s full height.
| Where | Country | Km from source | Water height, m | Inland, m | Measured by | First wave, UTC | Deaths |
|---|---|---|---|---|---|---|---|
| Simonstown (Simon'S Bay) | South Africa | 230 | 0.15 | Tide gauge (half the maximum wave height) | day 11, 10:50 | ||
| Mossel Bay (Mosselbaai) | South Africa | 234 | 0.29 | Tide gauge (half the maximum wave height) | day 11, 11:40 | ||
| Knysa | South Africa | 315 | 0.21 | Tide gauge (half the maximum wave height) | day 11, 12:15 | ||
| Saldanha Bay | South Africa | 359 | Tide gauge (half the maximum wave height) | day 11, 11:35 | |||
| Port Elizabeth | South Africa | 524 | 0.24 | Tide gauge (half the maximum wave height) | day 11, 14:35 | ||
| East London | South Africa | 760 | 0.14 | Tide gauge (half the maximum wave height) | day 11, 14:35 | ||
| Port Nolloth | South Africa | 761 | Tide gauge (half the maximum wave height) | ||||
| Luderitz | Namibia | 1,109 | Tide gauge (half the maximum wave height) | ||||
| Richards Bay | South Africa | 1,345 | 0.05 | Tide gauge (half the maximum wave height) | day 11, 14:35 |
More
Every tsunami in 1981The 1900sTsunamis of South AfricaThis day in weather historyAlerts in force
Sources
Tsunami events and runups from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-09-24. NCEI tsunami event 2129.