M4.2 Earthquake 112 km WNW of Houma, Tonga — March 21, 2026
2026-03-21 22:32:15 UTC (2026-03-21) · approx. 10:32 AM UTC-12 local
On March 21, 2026 at 22:32 UTC, a magnitude 4.2 intermediate depth earthquake struck 112 km WNW of Houma, Tonga, at a depth of 218.4 km and coordinates -20.9687°, -176.3607°.
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 5.2 mainshock that occurred 20 days ago 121 km WNW of Houma, Tonga. 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
-176.3607°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.2 earthquake near Houma, Tonga?
The magnitude 4.2 earthquake that struck 112 km WNW of Houma, Tonga on March 21, 2026 at 22:32 UTC had a depth of 218.4 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 M5.2 one earlier?
No. This magnitude 4.2 earthquake is an aftershock of the larger magnitude 5.2 mainshock that occurred earlier 121 km WNW of Houma, Tonga. 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.
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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: us7000s94p). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2026, March 21, 2026). M4.2 Earthquake 112 km WNW of Houma, Tonga — March 21, 2026. Retrieved May 13, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000s94p/