M2.6 earthquake 8km N of Petrolia, CA

A magnitude 2.6 earthquake struck 8km N of Petrolia, CA on Mon, Dec 20, 2021, 12:23 PM PST (20:23 UTC), 26 km (16 mi) below the surface.

A larger quake followed: M4.6 50km W 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
2.59	Md, duration	Northern California Seismic System	Preferred · Final · ±0.14 · 34 stations
2.5	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed · ±0.06 · 36 stations

1 person reported to the USGS what they felt.

Reviewed by a seismologist.

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

Within 100 km, magnitude 1.5 and up: at least 200 in the 60 days after this one and 40 in the 30 days before it.

The first 60 of at least 200.

From the USGS Earthquake Hazards Program and its partner networks, event nc73666261 (also filed as us6000gdxy). Read Sun, Oct 4, 2026, 4:43 PM UTC.