M5.1 Earthquake in the Kermadec Islands region — October 31, 2021
2021-10-31 09:18:14 UTC (2021-10-31) · approx. 9:18 PM UTC-12 local
Aftershock of the M5.5 mainshock.
On October 31, 2021 at 09:18 UTC, a magnitude 5.1 shallow crustal earthquake struck in the Kermadec Islands region, at a depth of 56.1 km and coordinates -28.1850°, -177.3475°.
Physical scale: An earthquake of magnitude 5.1 releases seismic energy equivalent to roughly 674 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 2.0 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 5.5 mainshock that occurred 10 hours 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
-177.3475°E
Technical Information
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Common Questions
How strong was the magnitude 5.1 earthquake in the Kermadec Islands region?
The magnitude 5.1 earthquake that struck in the Kermadec Islands region on October 31, 2021 at 09:18 UTC had a depth of 56.1 km. For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at -28.1850°, -177.3475°, which is in the Kermadec Islands region.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.1 earthquakes can continue for days to weeks and gradually diminish over time.
Is this the same earthquake as the M5.5 one earlier?
No. This magnitude 5.1 earthquake is an aftershock of the larger magnitude 5.5 mainshock that occurred earlier in the Kermadec Islands region. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Actions
Authoritative source: USGS event page (event ID: us7000fq97). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 31, 2021). M5.1 Earthquake in the Kermadec Islands region — October 31, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000fq97/