M4.5 Earthquake 49 km SE of Porto Martins, Portugal — December 17, 2025
2025-12-17 21:42:35 UTC (2025-12-17) · approx. 7:42 PM UTC-2 local
On December 17, 2025 at 21:42 UTC, a magnitude 4.5 shallow crustal earthquake struck 49 km SE of Porto Martins, Portugal, at a depth of 11.5 km and coordinates 38.3638°, -26.6536°. This earthquake was detected by 27 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.
Earthquake Details
-26.6536°E
Technical Information
Common Questions
How strong was the magnitude 4.5 earthquake near Porto Martins, Portugal?
The magnitude 4.5 earthquake that struck 49 km SE of Porto Martins, Portugal on December 17, 2025 at 21:42 UTC had a depth of 11.5 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 38.3638°, -26.6536°, which is 49 km SE of Porto Martins, Portugal.
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.
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: us7000rnqt). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, December 17, 2025). M4.5 Earthquake 49 km SE of Porto Martins, Portugal — December 17, 2025. Retrieved May 24, 2026 from https://www.earthquaketracker.org/earthquakes/event/us7000rnqt/