M2.7 earthquake 18km W of Petrolia, CA

A magnitude 2.7 earthquake struck 18km W of Petrolia, CA on Tue, Apr 20, 2021, 7:08 AM PDT (14:08 UTC), 23 km (14 mi) below the surface.

A larger quake followed: M2.9 8km W of Redway, 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
2.66	Md, duration	Northern California Seismic System	Preferred · Final · ±0.203 · 29 stations
2.1	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed · ±0.065 · 31 stations

1 person reported to the USGS what they felt; the strongest reported shaking was III, 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: 59 in the 60 days after this one and 36 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event nc73552115 (also filed as us6000e37c). Read Sun, Oct 4, 2026, 3:08 PM UTC.