M4.6 Earthquake 21 km ENE of Santa Maria, Philippines — October 1, 2023
2023-10-01 22:54:27 UTC (2023-10-01) · approx. 6:54 AM UTC+8 local
Aftershock of the M5.3 mainshock.
On October 1, 2023 at 22:54 UTC, a magnitude 4.6 intermediate depth earthquake struck 21 km ENE of Santa Maria, Philippines, at a depth of 78.0 km and coordinates 8.0330°, 126.6357°. This earthquake was detected by 84 seismic stations with good 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 5.3 mainshock that occurred 27 days ago 16 km ENE of Baganga, 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
126.6357°E
Technical Information
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Common Questions
How strong was the magnitude 4.6 earthquake near Santa Maria, Philippines?
The magnitude 4.6 earthquake that struck 21 km ENE of Santa Maria, Philippines on October 1, 2023 at 22:54 UTC had a depth of 78.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 8.0330°, 126.6357°, which is 21 km ENE of Santa Maria, Philippines. View all earthquakes in Philippines.
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 M5.3 one earlier?
No. This magnitude 4.6 earthquake is an aftershock of the larger magnitude 5.3 mainshock that occurred earlier 16 km ENE of Baganga, 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 4.6 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000lc5l). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, October 1, 2023). M4.6 Earthquake 21 km ENE of Santa Maria, Philippines — October 1, 2023. Retrieved December 14, 2023 from https://www.earthquaketracker.org/earthquakes/event/us6000lc5l/