Reviewed by USGSSouth Africa40y ago
M5.3 earthquake 0 km NE of Orkney, South Africa
Tuesday, October 28, 1986, 15:04:21 UTC · 26.978°S, 26.676°E
A magnitude 5.3 earthquake struck 0 km NE of Orkney, South Africa on Tuesday, October 28, 1986, 15:04:21 UTC, at a depth of 5.0 km (shallow). It is the strongest earthquake within 300 km since an M5.5 on April 7, 1977.
- Magnitude
- 5.3
- Moderate · ms
- Depth
- 5 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VII
- Very strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
1 kilotons of TNT
That is about 1/11 of the Hiroshima bomb. It released about 3 times the energy of a magnitude 5.0.
Tectonic setting
8 km
from the nearest mapped plate boundary, between the Somali and African plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
5 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 75 km
USGS has not published any M2.5+ earthquake within 75 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 21 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.128 km N of Maputsoe, LesothoFebruary 20, 1912 · 217 km SE of this epicenter
- 5.712 km WNW of Westonaria, South AfricaMay 14, 1974 · 116 km NE of this epicenter
- 5.55 km NNW of Orkney, South AfricaApril 7, 1977 · 5 km N of this epicenter
- 5.28 km WNW of Welkom, South AfricaDecember 8, 1976 · 108 km S of this epicenter
- 5.212 km SE of Orkney, South AfricaDecember 19, 1973 · 13 km SE of this epicenter
- 5.227 km N of Klerksdorp, South AfricaSeptember 30, 1973 · 42 km N of this epicenter
- 5.23 km S of Klerksdorp, South AfricaJune 6, 1983 · 10 km N of this epicenter
- 5.137 km WNW of Randfontein, South AfricaOctober 1, 1973 · 128 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 1 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 4 recorded deaths. The most severe:
- 1976M5.2
South Africa
8 Dec 1976 · 108 km away
4 deathsModerate damage ($1–5M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.