M3.1 earthquake 6km WSW of St. Helena, CA

A magnitude 3.1 earthquake struck 6km WSW of St. Helena, CA on Thu, Mar 4, 2021, 7:53 AM PST (15:53 UTC), 11 km (7 mi) below the surface.

A larger quake followed: M4.0 3km SW of Anderson Springs, 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
3.09	ML, local (Richter)	Northern California Seismic System	Preferred · Final · ±0.208 · 60 stations
2.8	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed · ±0.04 · 81 stations

234 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: 171 in the 60 days after this one and 83 in the 30 days before it.

The first 60 of 171.

From the USGS Earthquake Hazards Program and its partner networks, event nc73531186 (also filed as us7000dfh3). Read Sun, Oct 4, 2026, 1:47 PM UTC.