M4.9 Earthquake in the South Sandwich Islands region — September 25, 2023
2023-09-25 04:12:20 UTC (2023-09-25) · approx. 2:12 AM UTC-2 local
Felt by 1 person across nearby locations. Aftershock of the M5.0 mainshock.
On September 25, 2023 at 04:12 UTC, a magnitude 4.9 intermediate depth earthquake struck in the South Sandwich Islands region, at a depth of 156.2 km and coordinates -55.9123°, -28.3764°. This earthquake was detected by 79 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 369, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.9 releases seismic energy equivalent to roughly 338 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.4 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 5.0 mainshock that occurred 23 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 days to weeks 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
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 1 citizen response to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
-28.3764°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.9 earthquake in the South Sandwich Islands region?
The magnitude 4.9 earthquake that struck in the South Sandwich Islands region on September 25, 2023 at 04:12 UTC had a depth of 156.2 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at -55.9123°, -28.3764°, which is in the South Sandwich Islands region.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.9 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.0 one earlier?
No. This magnitude 4.9 earthquake is an aftershock of the larger magnitude 5.0 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: us7000kxxd). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, September 25, 2023). M4.9 Earthquake in the South Sandwich Islands region — September 25, 2023. Retrieved December 9, 2023 from https://www.earthquaketracker.org/earthquakes/event/us7000kxxd/