California earthquakes

M3.6 earthquake 35km W of Petrolia, CA

A magnitude 3.6 earthquake struck 35km W of Petrolia, CA on Fri, Dec 24, 2021, 6:24 AM PST (14:24 UTC), 23 km (14 mi) below the surface.

A larger quake followed: M4.6 50km W of Petrolia, CA. This one was a foreshock.

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Map

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

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The earthquake

Magnitude: 3.6 (Mw, moment), minor
Magnitude from: Northern California Seismic System
Local time: Fri, Dec 24, 2021, 6:24 AM PST
UTC: 2021-12-24 14:24:25 UTC
Depth: 23.0 km (14.3 mi), shallow
Epicenter: 40.321° N, 124.700° W
Region: California
Felt reports: 1
Strongest shaking: II, weak shaking
Tsunami flag: No
Status: Reviewed by a seismologist

Magnitude estimates

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
3.6	Mw, moment	Northern California Seismic System	Preferred · Final · 3 stations
3.6	Mwr, regional moment	USGS National Earthquake Information Center	Reviewed · 3 stations
4.2	Mw, moment	EW	Preliminary · ±0.3 · 8 stations

Shaking

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

Strongest estimated: II, weak shaking
Peak ground acceleration: 0.1% of gravity
Peak ground velocity: -3.2 cm/s
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

Did you feel it?

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

Fault motion and ground failure

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Moment magnitude: 3.6 Mw

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 0.7 km horizontally, 1.9 km in depth
Depth from: From location
Station coverage gap: 261°, poorly surrounded by stations
Stations used: 27

Nearest places

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

Nearby

Within 100 km, magnitude 1.5 and up: 116 in the 60 days after this one and 173 in the 30 days before it.

After

The first 60 of 116.

Before

Earthquakes today California earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event nc73668291 (also filed as ew1640355870, us6000gf22). Read Sun, Oct 4, 2026, 3:15 PM UTC.