M4.2 Earthquake south of the Fiji Islands — July 23, 2023
2023-07-23 22:49:33 UTC (2023-07-23) · approx. 10:49 AM UTC-12 local
On July 23, 2023 at 22:49 UTC, a magnitude 4.2 deep-focus earthquake struck south of the Fiji Islands, at a depth of 509.3 km and coordinates -23.7145°, -179.9870°.
Physical scale: An earthquake of magnitude 4.2 releases seismic energy equivalent to roughly 30 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 476 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 5.5 mainshock that occurred 2 days ago south of the Fiji Islands. 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.
Earthquake Details
-179.9870°E
Technical Information
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Common Questions
How strong was the magnitude 4.2 earthquake south of the Fiji Islands?
The magnitude 4.2 earthquake that struck south of the Fiji Islands on July 23, 2023 at 22:49 UTC had a depth of 509.3 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 4.2 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.5 one earlier?
No. This magnitude 4.2 earthquake is an aftershock of the larger magnitude 5.5 mainshock that occurred earlier south of the Fiji Islands. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
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Understanding This Data
Magnitude 4.2 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: us6000kx29). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, July 23, 2023). M4.2 Earthquake south of the Fiji Islands — July 23, 2023. Retrieved September 30, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000kx29/