Reviewed by USGSSouth Africa12y ago
M5.4 earthquake 3 km ESE of Orkney, South Africa
Tuesday, August 5, 2014, 10:22:33 UTC · 26.990°S, 26.705°E
A magnitude 5.4 earthquake struck 3 km ESE of Orkney, South Africa on Tuesday, August 5, 2014, 10:22:33 UTC, at a depth of 5.0 km (shallow). USGS received 364 “Did You Feel It?” reports, with a maximum reported intensity of VII (very strong). The USGS PAGER alert is yellow: some casualties and damage are possible. It is the strongest earthquake within 300 km since an M5.7 on April 22, 1999.
- Magnitude
- 5.4
- Moderate · mwb
- Depth
- 5 km
- Shallow
- Felt reports
- 364
- Max intensity VII
- Est. shaking
- VII
- Very strong (ShakeMap)
- PAGER alert
- Yellow
- Impact estimate
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 75 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
2 kilotons of TNT
That is about 1/8 of the Hiroshima bomb. It released about 4 times the energy of a magnitude 5.0.
Tectonic setting
10 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
Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.
| Place | Intensity | Reports | Distance |
|---|---|---|---|
| Johannesburg, Gauteng, South Africa | IV · Light | 81 | 159 km |
| Midrand, Gauteng, South Africa | III · Weak | 62 | 179 km |
| Pretoria, Gauteng, South Africa | III · Weak | 37 | 205 km |
| Verwoerdburg, Gauteng, South Africa | III · Weak | 28 | 196 km |
| Durban, KwaZulu Natal, South Africa | III · Weak | 10 | 527 km |
| Boksburg, Gauteng, South Africa | III · Weak | 9 | 171 km |
| Benoni, Gauteng, South Africa | IV · Light | 8 | 186 km |
| Krugersdorp, Gauteng, South Africa | III · Weak | 8 | 145 km |
| Vanderbijlpark, Gauteng, South Africa | IV · Light | 7 | 115 km |
| Rustenburg, North West, South Africa | IV · Light | 5 | 157 km |
| Potchefstroom, North West, South Africa | V · Moderate | 4 | 50 km |
| Ballitoville, KwaZulu Natal, South Africa | III · Weak | 4 | 523 km |
USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No populated area was estimated to feel noticeable shaking.
After the main event
Aftershocks within 75 km
USGS lists 6 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M4.7 on August 30, 2014. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.712 km SE of Stilfontein, South Africa12y ago · 18 km NE of this epicenter
- 4.68 km E of Orkney, South Africa12y ago · 5 km E of this epicenter
- 4.68 km NE of Orkney, South Africa12y ago · 8 km N of this epicenter
- 4.63 km NNW of Klerksdorp, South Africa12y ago · 19 km N of this epicenter
- 4.37 km S of Stilfontein, South Africa12y ago · 12 km NE of this epicenter
- 4.44 km W of Stilfontein, South Africa12y ago · 17 km N of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 38 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 · 214 km SE of this epicenter
- 5.712 km WNW of Westonaria, South AfricaMay 14, 1974 · 115 km NE of this epicenter
- 5.710 km WNW of Welkom, South AfricaApril 22, 1999 · 107 km S of this epicenter
- 5.66 km S of Welkom, South AfricaOctober 30, 1994 · 116 km S of this epicenter
- 5.55 km NNW of Orkney, South AfricaApril 7, 1977 · 8 km NW of this epicenter
- 5.50 km S of Welkom, South AfricaJanuary 25, 1989 · 111 km S of this epicenter
- 5.35 km SSE of Welkom, South AfricaJune 6, 1992 · 115 km S of this epicenter
- 5.30 km NE of Orkney, South AfricaOctober 28, 1986 · 3 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 7 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 36 recorded deaths. The most severe:
- 1997M5.0
Avgold'S Hartebeestfontein Mine
21 Jul 1997 · 17 km away
15 deaths
- 1990M4.0
Charletonville
18 Oct 1990 · 92 km away
10 deaths
- 1976M5.2
South Africa
8 Dec 1976 · 107 km away
4 deathsModerate damage ($1–5M)
- 2005M4.3
Klerksdorp, Stilfontein
9 Mar 2005 · 12 km away
2 deathsModerate damage ($1–5M)
- 1990M4.2
Welkom
26 Sep 1990 · 114 km away
2 deathsLimited damage (under $1M)
- 2009M3.5
Carletonville
6 Dec 2009 · 101 km away
2 deaths
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.