M3.9 Earthquake 54 km W of Petrolia, CA — September 9, 2025
2025-09-09 19:40:59 UTC (2025-09-09) · approx. 11:40 AM UTC-8 local
Felt by 13 people across nearby locations.
On September 9, 2025 at 19:40 UTC, a magnitude 3.9 shallow crustal earthquake struck 54 km W of Petrolia, CA, at a depth of 6.5 km and coordinates 40.3318°, -124.9268°. The earthquake was reported felt by 13 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 2.7 (weak). This earthquake was detected by 152 seismic stations with moderate location accuracy and was assigned a USGS significance rating of 237, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 3.9 releases seismic energy equivalent to roughly 10.0 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 287 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in California, a region characterized by the San Andreas transform fault system, where the Pacific and North American plates slide past each other at roughly 46 mm per year. The nearest mapped fault system is the San Andreas Fault. View all earthquakes in California.
Learn more: San Andreas Fault · Magnitude scale · Aftershock sequences
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 13 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
-124.9268°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 3.9 earthquake near Petrolia, CA?
The magnitude 3.9 earthquake that struck 54 km W of Petrolia, CA on September 9, 2025 at 19:40 UTC had a depth of 6.5 km. It was felt by 13 people with maximum shaking intensity of MMI 2.7 (weak). For context, this was a minor earthquake typically detected only by instruments.
Where did the earthquake occur?
The earthquake epicenter was located at 40.3318°, -124.9268°, which is 54 km W of Petrolia, CA. View all earthquakes in California.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.9 earthquakes can continue for several days and gradually diminish over time.
Has California had earthquakes this big before?
The largest recorded earthquake in California was the M7.9 Fort Tejon earthquake of January 9, 1857. Today's magnitude 3.9 event is significantly smaller than that historical record.
Actions
Authoritative source: USGS event page (event ID: nc75235672). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, September 9, 2025). M3.9 Earthquake 54 km W of Petrolia, CA — September 9, 2025. Retrieved November 30, 2025 from https://www.earthquaketracker.org/earthquakes/event/nc75235672/