Reviewed by USGS7y ago
M7.1 earthquake in South Sandwich Islands region
Tuesday, December 11, 2018, 02:26:29 UTC · 58.545°S, 26.386°W
A magnitude 7.1 earthquake struck in South Sandwich Islands region on Tuesday, December 11, 2018, 02:26:29 UTC, at a depth of 133.0 km (intermediate). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.2 on May 28, 2016.
Tsunami flagUSGS sets this flag for large events in oceanic regions so tsunami warning centers review them. It does not by itself mean a tsunami occurred. Check tsunami.gov and local authorities for official messages.
- Magnitude
- 7.1
- Major · mww
- Depth
- 133 km
- Intermediate
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- V
- Moderate (ShakeMap)
- PAGER alert
- Green
- Impact estimate
- Tsunami
- Flag
- Check tsunami.gov
Outlined circle: this earthquakeDashed circle: 200 km aftershock search area
In context
How big was it, and why here?
Energy released
674 kilotons of TNT
That is about 45 times the Hiroshima bomb. It released about 1,413 times the energy of a magnitude 5.0.
Tectonic setting
142 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
133 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 populated area was estimated to feel noticeable shaking.
After the main event
Aftershocks within 200 km
USGS lists 6 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.4 on January 3, 2019. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 4.7South Sandwich Islands region7y ago · 140 km S of this epicenter
- 5.4South Sandwich Islands region7y ago · 134 km S of this epicenter
- 4.5South Sandwich Islands region7y ago · 62 km SE of this epicenter
- 5.2South Sandwich Islands region7y ago · 86 km NE of this epicenter
- 4.4South Sandwich Islands region7y ago · 91 km N of this epicenter
- 4.6South Sandwich Islands region7y ago · 184 km NE of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,289 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8South Sandwich Islands regionMay 26, 1964 · 258 km N of this epicenter
- 7.5South Sandwich Islands regionAugust 28, 1933 · 194 km S of this epicenter
- 7.3South Sandwich Islands regionSeptember 1, 1961 · 85 km S of this epicenter
- 7.3South Sandwich Islands regionJuly 15, 2013 · 267 km S of this epicenter
- 7.2South Sandwich Islands regionNovember 15, 1910 · 154 km SE of this epicenter
- 7.2South Sandwich Islands regionDecember 27, 1991 · 287 km N of this epicenter
- 7.2South Sandwich Islands regionOctober 22, 1983 · 242 km S of this epicenter
- 7.2South Sandwich Islands regionMay 28, 2016 · 258 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 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 · 70 km away
- 1961M7.7
South Sandwich Islands
8 Sep 1961 · 260 km away
- 1961M7.5
South Sandwich Islands
1 Sep 1961 · 118 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.