M4.4 Earthquake in the South Sandwich Islands region — July 20, 2021
2021-07-20 22:10:16 UTC (2021-07-20) · approx. 8:10 PM UTC-2 local
On July 20, 2021 at 22:10 UTC, a magnitude 4.4 intermediate depth earthquake struck in the South Sandwich Islands region, at a depth of 96.6 km and coordinates -55.9337°, -27.5235°.
Physical scale: An earthquake of magnitude 4.4 releases seismic energy equivalent to roughly 60 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 655 m — 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 23 days ago in the South Sandwich Islands region. Since the mainshock, the USGS has recorded 1 aftershocks in this area. Aftershock activity is expected to continue for weeks to months as stresses on surrounding faults redistribute.
Earthquake Details
-27.5235°E
Technical Information
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Common Questions
How strong was the magnitude 4.4 earthquake in the South Sandwich Islands region?
The magnitude 4.4 earthquake that struck in the South Sandwich Islands region on July 20, 2021 at 22:10 UTC had a depth of 96.6 km. For context, this was a light earthquake commonly felt near the epicenter.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.4 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M6.2 one earlier?
No. This magnitude 4.4 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.
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Understanding This Data
Magnitude 4.4 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us6000ezf1). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, July 20, 2021). M4.4 Earthquake in the South Sandwich Islands region — July 20, 2021. Retrieved September 25, 2021 from https://www.earthquaketracker.org/earthquakes/event/us6000ezf1/