M4.6 Earthquake in the Kermadec Islands region — September 20, 2025
2025-09-20 16:56:17 UTC (2025-09-20) · approx. 4:56 AM UTC-12 local
Aftershock of the M5.0 mainshock.
On September 20, 2025 at 16:56 UTC, a magnitude 4.6 shallow crustal earthquake struck in the Kermadec Islands region, at a depth of 39.2 km and coordinates -31.8714°, -178.6489°. This earthquake was detected by 25 seismic stations with moderate location accuracy and was assigned a USGS significance rating of 326, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.6 releases seismic energy equivalent to roughly 120 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 899 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 5.0 mainshock that occurred 12 days ago in the Kermadec Islands region. 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
-178.6489°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.6 earthquake in the Kermadec Islands region?
The magnitude 4.6 earthquake that struck in the Kermadec Islands region on September 20, 2025 at 16:56 UTC had a depth of 39.2 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at -31.8714°, -178.6489°, which is in the Kermadec Islands region.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.6 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.0 one earlier?
No. This magnitude 4.6 earthquake is an aftershock of the larger magnitude 5.0 mainshock that occurred earlier in the Kermadec Islands region. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
What should I do after an earthquake?
If you were in the affected area: check yourself and others for injuries, inspect your home for damage, and be prepared for aftershocks. For detailed guidance, see our earthquake safety guide and emergency planning resources.
Authoritative source: USGS event page (event ID: us7000qxkx). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, September 20, 2025). M4.6 Earthquake in the Kermadec Islands region — September 20, 2025. Retrieved May 28, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000qxkx/