M3.1 earthquake 11km N of Petrolia, CA

A magnitude 3.1 earthquake struck 11km N of Petrolia, CA on Mon, Dec 20, 2021, 12:55 PM PST (20:55 UTC), 25 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
3.07	ML, local (Richter)	Northern California Seismic System	Preferred · Final · ±0.206 · 23 stations
2.9	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed · ±0.042 · 76 stations

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

2 people reported to the USGS what they felt; the strongest reported shaking was IV, light 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: at least 200 in the 60 days after this one and 61 in the 30 days before it.

The first 60 of at least 200.

From the USGS Earthquake Hazards Program and its partner networks, event nc73666376 (also filed as us6000gdyl). Read Sun, Oct 4, 2026, 12:35 PM UTC.