M4.8 Earthquake 281 km SSE of Ushuaia, Argentina — July 21, 2026
2026-07-21 17:21:06 UTC (2 hours ago) · approx. 1:21 PM UTC-4 local
Aftershock of the M5.8 mainshock.
On July 21, 2026 at 17:21 UTC, a magnitude 4.8 shallow crustal earthquake struck 281 km SSE of Ushuaia, Argentina, at a depth of 10.0 km and coordinates -57.1718°, -66.6861°. This earthquake was detected by 44 seismic stations with good location accuracy and was assigned a USGS significance rating of 354, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.8 releases seismic energy equivalent to roughly 239 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.2 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 5.8 mainshock that occurred 14 days ago 296 km SSE of Ushuaia, Argentina. Since the mainshock, the USGS has recorded 2 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
Earthquake Details
-66.6861°E
Technical Information
Common Questions
How strong was the magnitude 4.8 earthquake near Ushuaia, Argentina?
The magnitude 4.8 earthquake that struck 281 km SSE of Ushuaia, Argentina on July 21, 2026 at 17:21 UTC had a depth of 10.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at -57.1718°, -66.6861°, which is 281 km SSE of Ushuaia, Argentina.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.8 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.8 one earlier?
No. This magnitude 4.8 earthquake is an aftershock of the larger magnitude 5.8 mainshock that occurred earlier 296 km SSE of Ushuaia, Argentina. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Authoritative source: USGS event page (event ID: us7000t29r). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2026, July 21, 2026). M4.8 Earthquake 281 km SSE of Ushuaia, Argentina — July 21, 2026. Retrieved July 21, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000t29r/