Reviewed by USGS5y ago
M4.6 earthquake in South Sandwich Islands region
Saturday, September 11, 2021, 05:09:08 UTC · 60.399°S, 26.707°W
A magnitude 4.6 earthquake struck in South Sandwich Islands region on Saturday, September 11, 2021, 05:09:08 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M5.0 on September 10, 2021.
- Magnitude
- 4.6
- Light · mb
- Depth
- 10 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
9 km
from the nearest mapped plate boundary, between the Sandwich and Antarctic plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
10 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 50 km
USGS lists 17 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M6.2 on October 4, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.0South Sandwich Islands region5y ago · 40 km NW of this epicenter
- 4.7South Sandwich Islands region5y ago · 37 km W of this epicenter
- 4.3South Sandwich Islands region5y ago · 8 km SE of this epicenter
- 4.6South Sandwich Islands region5y ago · 28 km NW of this epicenter
- 4.7South Sandwich Islands region5y ago · 13 km S of this epicenter
- 4.8South Sandwich Islands region5y ago · 17 km W of this epicenter
- 4.9South Sandwich Islands region5y ago · 45 km W of this epicenter
- 5.1South Sandwich Islands region5y ago · 22 km W of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 870 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.12021 South Sandwich Islands EarthquakeAugust 12, 2021 · 239 km N of this epicenter
- 7.5South Sandwich Islands regionAugust 28, 1933 · 27 km NW of this epicenter
- 7.4east of the South Sandwich IslandsJanuary 2, 2006 · 285 km E of this epicenter
- 7.3South Sandwich Islands regionSeptember 1, 1961 · 125 km N of this epicenter
- 7.3South Sandwich Islands regionJuly 15, 2013 · 103 km SE of this epicenter
- 7.2South Sandwich Islands regionNovember 15, 1910 · 211 km NE of this epicenter
- 7.2South Sandwich Islands regionOctober 22, 1983 · 75 km SE of this epicenter
- 7.1South Sandwich Islands regionAugust 22, 2021 · 102 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 2021M8.1
South Sandwich Islands
12 Aug 2021 · 234 km away
tsunami
- 1961M7.7
South Sandwich Islands
5 Sep 1961 · 267 km away
- 1961M7.5
South Sandwich Islands
1 Sep 1961 · 105 km away
- 1973M7.5
Antarctica
6 Oct 1973 · 285 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.