M4.5 Earthquake 11 km SSE of Union, Philippines — October 16, 2025
2025-10-16 23:20:23 UTC (2025-10-16) · approx. 7:20 AM UTC+8 local
Aftershock of the M5.5 mainshock.
On October 16, 2025 at 23:20 UTC, a magnitude 4.5 shallow crustal earthquake struck 11 km SSE of Union, Philippines, at a depth of 17.2 km and coordinates 9.6582°, 126.1559°. This earthquake was detected by 18 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 5.5 mainshock that occurred 2 days ago 13 km E of Cortes, Philippines. 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.
The epicenter is located in Philippines, a region characterized by the Manila Trench and Philippine Trench subduction systems, where the Philippine Sea Plate overrides the Eurasian Plate. The nearest mapped fault system is the Philippine Fault. View all earthquakes in Philippines.
Learn more: Magnitude scale · Aftershock sequences
Earthquake Details
126.1559°E
Technical Information
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Common Questions
How strong was the magnitude 4.5 earthquake near Union, Philippines?
The magnitude 4.5 earthquake that struck 11 km SSE of Union, Philippines on October 16, 2025 at 23:20 UTC had a depth of 17.2 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 9.6582°, 126.1559°, which is 11 km SSE of Union, Philippines. View all earthquakes in Philippines.
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 M5.5 one earlier?
No. This magnitude 4.5 earthquake is an aftershock of the larger magnitude 5.5 mainshock that occurred earlier 13 km E of Cortes, Philippines. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Has Philippines had earthquakes this big before?
The largest recorded earthquake in Philippines was the M8.0 Mindanao earthquake of August 17, 1976. Today's magnitude 4.5 event is significantly smaller than that historical record.
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: us6000rlx5). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, October 16, 2025). M4.5 Earthquake 11 km SSE of Union, Philippines — October 16, 2025. Retrieved May 27, 2026 from https://www.earthquaketracker.org/earthquakes/event/us6000rlx5/