M5.9 Earthquake east of the South Sandwich Islands — July 4, 2023
2023-07-04 12:01:01 UTC (2023-07-04) · approx. 11:01 AM UTC-1 local
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On July 4, 2023 at 12:01 UTC, a magnitude 5.9 shallow crustal earthquake struck east of the South Sandwich Islands, at a depth of 10.0 km and coordinates -58.1291°, -12.8468°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 64 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 536, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 5.9 releases seismic energy equivalent to roughly 11 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 7.1 km — a useful intuition for the size of the slip patch on the fault.
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
-12.8468°E
Technical Information
Common Questions
How strong was the magnitude 5.9 earthquake east of the South Sandwich Islands?
The magnitude 5.9 earthquake that struck east of the South Sandwich Islands on July 4, 2023 at 12:01 UTC had a depth of 10.0 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at -58.1291°, -12.8468°, which is east of the South Sandwich Islands.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.9 earthquakes can continue for days to weeks and gradually diminish over time.
Actions
Authoritative source: USGS event page (event ID: us6000kq0u). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, July 4, 2023). M5.9 Earthquake east of the South Sandwich Islands — July 4, 2023. Retrieved September 9, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kq0u/