M5.7 Earthquake in the South Sandwich Islands region — December 30, 2021
2021-12-30 04:58:15 UTC (2021-12-30) · approx. 2:58 AM UTC-2 local
Aftershock of the M6.2 mainshock.
On December 30, 2021 at 04:58 UTC, a magnitude 5.7 shallow crustal earthquake struck in the South Sandwich Islands region, at a depth of 41.0 km and coordinates -55.8888°, -28.0832°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected.
Physical scale: An earthquake of magnitude 5.7 releases seismic energy equivalent to roughly 5 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 5.2 km — a useful intuition for the size of the slip patch on the fault.
This earthquake is part of an ongoing aftershock sequence following the magnitude 6.2 mainshock that occurred 13 days ago in the South Sandwich Islands region. Since the mainshock, the USGS has recorded 0 aftershocks in this area. Aftershock activity is expected to continue for weeks to months as stresses on surrounding faults redistribute.
The epicenter is located in South Sandwich Islands, a region characterized by the South Sandwich Trench, one of Earth's most remote subduction zones.
Learn more: Magnitude scale · Aftershock sequences
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Earthquake Details
-28.0832°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 5.7 earthquake in the South Sandwich Islands region?
The magnitude 5.7 earthquake that struck in the South Sandwich Islands region on December 30, 2021 at 04:58 UTC had a depth of 41.0 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at -55.8888°, -28.0832°, which is in the South Sandwich Islands region.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.7 earthquakes can continue for days to weeks and gradually diminish over time.
Is this the same earthquake as the M6.2 one earlier?
No. This magnitude 5.7 earthquake is an aftershock of the larger magnitude 6.2 mainshock that occurred earlier in the South Sandwich Islands region. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Actions
Authoritative source: USGS event page (event ID: us7000g7w5). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, December 30, 2021). M5.7 Earthquake in the South Sandwich Islands region — December 30, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000g7w5/