M4.5 Earthquake in the Balleny Islands region — September 27, 2023
2023-09-27 21:27:14 UTC (2023-09-27) · approx. 7:27 AM UTC+10 local
Aftershock of the M5.9 mainshock.
On September 27, 2023 at 21:27 UTC, a magnitude 4.5 shallow crustal earthquake struck in the Balleny Islands region, at a depth of 10.0 km and coordinates -61.3586°, 154.8163°. This earthquake was detected by 15 seismic stations with good location accuracy and was assigned a USGS significance rating of 312, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.5 releases seismic energy equivalent to roughly 85 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 767 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 5.9 mainshock that occurred 3 days ago west of Macquarie Island. 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
154.8163°E
Technical Information
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Common Questions
How strong was the magnitude 4.5 earthquake in the Balleny Islands region?
The magnitude 4.5 earthquake that struck in the Balleny Islands region on September 27, 2023 at 21:27 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 -61.3586°, 154.8163°, which is in the Balleny Islands region.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.5 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.9 one earlier?
No. This magnitude 4.5 earthquake is an aftershock of the larger magnitude 5.9 mainshock that occurred earlier west of Macquarie Island. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Actions
Authoritative source: USGS event page (event ID: us6000lcg7). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, September 27, 2023). M4.5 Earthquake in the Balleny Islands region — September 27, 2023. Retrieved December 9, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000lcg7/