Reviewed by USGS5y ago
M6.2 earthquake in South Sandwich Islands region
Monday, October 4, 2021, 03:54:06 UTC · 60.416°S, 27.519°W
A magnitude 6.2 earthquake struck in South Sandwich Islands region on Monday, October 4, 2021, 03:54:06 UTC, at a depth of 10.0 km (shallow). USGS received 3 “Did You Feel It?” reports, with a maximum reported intensity of VII (very strong). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.1 on August 22, 2021.
- Magnitude
- 6.2
- Strong · mww
- Depth
- 10 km
- Shallow
- Felt reports
- 3
- Max intensity VII
- Est. shaking
- IV
- Light (ShakeMap)
- PAGER alert
- Green
- Impact estimate
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
30 kilotons of TNT
That is about 2 times the Hiroshima bomb. It released about 63 times the energy of a magnitude 5.0.
Tectonic setting
12 km
from the nearest mapped plate boundary, between the Sandwich and Scotia 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
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 |
|---|---|---|---|
| Grytviken, South Georgia, Falkland Islands | I · Not felt | 1 | 876 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 100 km
USGS lists 11 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.1 on October 4, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.5South Sandwich Islands region5y ago · 94 km NE of this epicenter
- 4.7South Sandwich Islands region5y ago · 88 km NE of this epicenter
- 4.5South Sandwich Islands region5y ago · 91 km NE of this epicenter
- 4.0South Sandwich Islands region5y ago · 24 km NE of this epicenter
- 4.7South Sandwich Islands region5y ago · 14 km NE of this epicenter
- 4.3South Sandwich Islands region5y ago · 51 km E of this epicenter
- 4.6South Sandwich Islands region5y ago · 34 km NE of this epicenter
- 4.7South Sandwich Islands region5y ago · 47 km E of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 802 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 · 260 km NE of this epicenter
- 7.5South Sandwich Islands regionAugust 28, 1933 · 30 km NE of this epicenter
- 7.3South Sandwich Islands regionSeptember 1, 1961 · 133 km N of this epicenter
- 7.3South Sandwich Islands regionJuly 15, 2013 · 142 km E of this epicenter
- 7.2South Sandwich Islands regionNovember 15, 1910 · 247 km NE of this epicenter
- 7.2South Sandwich Islands regionOctober 22, 1983 · 116 km E of this epicenter
- 7.1South Sandwich Islands regionAugust 22, 2021 · 146 km E of this epicenter
- 7.1South Sandwich Islands regionDecember 11, 2018 · 218 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 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 · 255 km away
tsunami
- 1961M7.7
South Sandwich Islands
5 Sep 1961 · 270 km away
- 1961M7.5
South Sandwich Islands
1 Sep 1961 · 103 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.