Reviewed by USGS5y ago
M4.5 earthquake in South Sandwich Islands region
Tuesday, September 28, 2021, 19:04:21 UTC · 59.400°S, 25.627°W
A magnitude 4.5 earthquake struck in South Sandwich Islands region on Tuesday, September 28, 2021, 19:04:21 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M4.6 on September 28, 2021.
- Magnitude
- 4.5
- Light · mb
- Depth
- 35 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
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
58 km
from the nearest mapped plate boundary, between the Sandwich and South American plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
35 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 16 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.1 on September 29, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.9South Sandwich Islands region4y ago · 24 km SW of this epicenter
- 5.0South Sandwich Islands region4y ago · 39 km E of this epicenter
- 4.5South Sandwich Islands region5y ago · 48 km SW of this epicenter
- 4.5South Sandwich Islands region5y ago · 34 km NE of this epicenter
- 4.3South Sandwich Islands region5y ago · 23 km SW of this epicenter
- 4.9South Sandwich Islands region5y ago · 45 km SW of this epicenter
- 4.2South Sandwich Islands region5y ago · 14 km W of this epicenter
- 4.7South Sandwich Islands region5y ago · 49 km SW of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,096 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 · 116 km N of this epicenter
- 7.5South Sandwich Islands regionAugust 12, 2021 · 207 km N of this epicenter
- 7.5South Sandwich Islands regionAugust 28, 1933 · 125 km SW of this epicenter
- 7.4east of the South Sandwich IslandsJanuary 2, 2006 · 282 km SE of this epicenter
- 7.3South Sandwich Islands regionSeptember 1, 1961 · 68 km W of this epicenter
- 7.3South Sandwich Islands regionJuly 15, 2013 · 165 km S of this epicenter
- 7.2South Sandwich Islands regionNovember 15, 1910 · 101 km E of this epicenter
- 7.2South Sandwich Islands regionOctober 22, 1983 · 141 km S 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 · 111 km away
tsunami
- 1961M7.7
South Sandwich Islands
5 Sep 1961 · 175 km away
- 1961M7.5
South Sandwich Islands
1 Sep 1961 · 95 km away
- 1973M7.5
Antarctica
6 Oct 1973 · 276 km away
- 2021M7.5
South Sandwich Islands
12 Aug 2021 · 202 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.