Reviewed by USGS5y ago
M4.5 earthquake in South Sandwich Islands region
Sunday, October 17, 2021, 02:36:53 UTC · 58.497°S, 25.614°W
A magnitude 4.5 earthquake struck in South Sandwich Islands region on Sunday, October 17, 2021, 02:36:53 UTC, at a depth of 78.1 km (intermediate). It is the strongest earthquake within 300 km since an M5.0 on October 16, 2021.
- Magnitude
- 4.5
- Light · mb
- Depth
- 78 km
- Intermediate
- 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
85 tons of TNT
That is about 1/178 of the Hiroshima bomb. A magnitude 5.0 releases about 6 times more energy.
Tectonic setting
100 km
from the nearest mapped plate boundary, between the Sandwich and South American plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: intermediate
78 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 7 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.6 on November 15, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.6South Sandwich Islands region4y ago · 34 km NE of this epicenter
- 4.5South Sandwich Islands region4y ago · 49 km SE of this epicenter
- 4.5South Sandwich Islands region4y ago · 43 km SE of this epicenter
- 4.6South Sandwich Islands region4y ago · 28 km N of this epicenter
- 4.2South Sandwich Islands region4y ago · 44 km NE of this epicenter
- 4.4South Sandwich Islands region4y ago · 25 km SE of this epicenter
- 4.4South Sandwich Islands region5y ago · 35 km S of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,574 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 · 24 km NE of this epicenter
- 7.8South Sandwich Islands regionMay 26, 1964 · 271 km NW of this epicenter
- 7.5South Sandwich Islands regionAugust 12, 2021 · 109 km N of this epicenter
- 7.5South Sandwich Islands regionAugust 28, 1933 · 212 km SW of this epicenter
- 7.3South Sandwich Islands regionSeptember 1, 1961 · 110 km SW of this epicenter
- 7.3South Sandwich Islands regionJuly 15, 2013 · 264 km S of this epicenter
- 7.2South Sandwich Islands regionNovember 15, 1910 · 118 km SE of this epicenter
- 7.2South Sandwich Islands regionDecember 27, 1991 · 275 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 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 · 19 km away
tsunami
- 1961M7.7
South Sandwich Islands
5 Sep 1961 · 98 km away
- 1961M7.7
South Sandwich Islands
8 Sep 1961 · 268 km away
- 1961M7.5
South Sandwich Islands
1 Sep 1961 · 148 km away
- 2021M7.5
South Sandwich Islands
12 Aug 2021 · 103 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.