Reviewed by USGS66y ago
M7.3 earthquake in South Sandwich Islands region
Friday, September 1, 1961, 00:09:39 UTC · 59.274°S, 26.801°W
A magnitude 7.3 earthquake struck in South Sandwich Islands region on Friday, September 1, 1961, 00:09:39 UTC, at a depth of 129.2 km (intermediate). It is the strongest earthquake within 300 km since an M7.5 on August 28, 1933.
- Magnitude
- 7.3
- Major · mw
- Depth
- 129 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: 200 km aftershock search area
In context
How big was it, and why here?
Energy released
1.3 megatons of TNT
That is about 89 times the Hiroshima bomb. It released about 2,818 times the energy of a magnitude 5.0.
Tectonic setting
86 km
from the nearest mapped plate boundary, between the Australian and Antarctic plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: intermediate
129 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 200 km
USGS lists 1 M2.5+ earthquake within 200 km in the following 30 days; the largest was M6.1 on September 27, 1961. 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 37 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.5South Sandwich Islands regionAugust 28, 1933 · 110 km S of this epicenter
- 7.2South Sandwich Islands regionNovember 15, 1910 · 164 km E of this epicenter
- 7.0South Sandwich Islands regionDecember 14, 1959 · 79 km S of this epicenter
- 7.0South Sandwich Islands regionMarch 9, 1943 · 162 km SW of this epicenter
- 7.0South Sandwich Islands regionMarch 21, 1926 · 248 km SE of this epicenter
- 6.8South Sandwich Islands regionNovember 2, 1943 · 283 km N of this epicenter
- 6.7east of the South Sandwich IslandsDecember 27, 1949 · 296 km E of this epicenter
- 6.6South Sandwich Islands regionFebruary 15, 1959 · 58 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 2 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1961M7.7
South Sandwich Islands
5 Sep 1961 · 142 km away
- 1961M7.5
South Sandwich Islands
1 Sep 1961 · 38 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.