Reviewed by USGS49y ago
M4.8 earthquake east of the South Sandwich Islands
Friday, August 26, 1977, 22:38:59 UTC · 59.483°S, 20.166°W
A magnitude 4.8 earthquake struck east of the South Sandwich Islands on Friday, August 26, 1977, 22:38:59 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M7.1 on August 26, 1977.
- Magnitude
- 4.8
- Light · mb
- Depth
- 33 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
239 tons of TNT
That is about 1/63 of the Hiroshima bomb. A magnitude 5.0 releases about 2 times more energy.
Tectonic setting
85 km
from the nearest mapped plate boundary, between the Pacific and Australian plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
33 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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.2 on September 5, 1977. 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 49 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.2South Sandwich Islands regionNovember 15, 1910 · 218 km W of this epicenter
- 7.1east of the South Sandwich IslandsAugust 26, 1977 · 20 km W of this epicenter
- 7.0east of the South Sandwich IslandsOctober 6, 1973 · 167 km SW of this epicenter
- 7.0South Sandwich Islands regionMarch 21, 1926 · 259 km SW of this epicenter
- 6.7South Sandwich Islands regionAugust 22, 1967 · 274 km SW of this epicenter
- 6.7South Sandwich Islands regionJanuary 14, 1936 · 186 km SW of this epicenter
- 6.7east of the South Sandwich IslandsDecember 27, 1949 · 109 km SW of this epicenter
- 6.6east of the South Sandwich IslandsMarch 18, 1933 · 291 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 1 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1973M7.5
Antarctica
6 Oct 1973 · 167 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.