M2.8 earthquake 7km WSW of Petrolia, CA

A magnitude 2.8 earthquake struck 7km WSW of Petrolia, CA on Wed, Sep 29, 2021, 11:37 PM PDT (06:37 UTC), 30 km (19 mi) below the surface.

A larger quake followed: M4.4 5km NNE of Petrolia, CA. This one was a foreshock.

Map

Where this earthquake was located, with the others nearby. Select one for its page.

Different scales measure different things and differ by a few tenths. The USGS marks one as preferred, and it is the one this page uses.

Mag.	Scale	Computed by	Notes
2.76	ML, local (Richter)	Northern California Seismic System	Preferred · Final · ±0.305 · 13 stations
2.8	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed · ±0.045 · 66 stations

1 person reported to the USGS what they felt; the strongest reported shaking was II, weak shaking.

Reviewed by a seismologist.

Distance and direction from each place to the epicenter, with its forecast.

Within 100 km, magnitude 1.5 and up: 55 in the 60 days after this one and 38 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event nc73631296 (also filed as us6000fqdh). Read Sun, Oct 4, 2026, 4:56 PM UTC.