Reviewed by USGS5y ago
M4.4 earthquake in South Sandwich Islands region
Friday, October 15, 2021, 09:49:27 UTC · 56.781°S, 26.809°W
A magnitude 4.4 earthquake struck in South Sandwich Islands region on Friday, October 15, 2021, 09:49:27 UTC, at a depth of 140.1 km (intermediate).
- Magnitude
- 4.4
- Light · mb
- Depth
- 140 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
60 tons of TNT
That is about 1/251 of the Hiroshima bomb. A magnitude 5.0 releases about 8 times more energy.
Tectonic setting
114 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
140 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.8 on November 3, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,605 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 · 200 km SE of this epicenter
- 8.11929 South Sandwich Islands EarthquakeJune 27, 1929 · 222 km NW of this epicenter
- 7.8South Sandwich Islands regionMay 26, 1964 · 73 km NW of this epicenter
- 7.5South Sandwich Islands regionAugust 12, 2021 · 138 km SE of this epicenter
- 7.3South Sandwich Islands regionSeptember 1, 1961 · 277 km S of this epicenter
- 7.2South Sandwich Islands regionDecember 27, 1991 · 126 km NE of this epicenter
- 7.2South Sandwich Islands regionMay 28, 2016 · 61 km N of this epicenter
- 7.1South Sandwich Islands regionSeptember 8, 1961 · 60 km NW 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:
- 1929M8.1
South Sandwich Islands
27 Jun 1929 · 222 km away
- 2021M8.1
South Sandwich Islands
12 Aug 2021 · 202 km away
tsunami
- 1961M7.7
South Sandwich Islands
5 Sep 1961 · 136 km away
- 1961M7.7
South Sandwich Islands
8 Sep 1961 · 65 km away
- 2021M7.5
South Sandwich Islands
12 Aug 2021 · 133 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.