M3.4 earthquake 3km SW of Redlands, CA

A magnitude 3.4 earthquake struck 3km SW of Redlands, CA on Fri, Dec 31, 2021, 11:27 AM PST (19:27 UTC), 14 km (9 mi) below the surface.

A larger quake followed: M4.0 5km WSW of Palomar Observatory, 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
3.38	ML, local (Richter)	Southern California Seismic Network	Preferred · Final · ±0.141 · 237 stations
3.2	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed · ±0.036 · 102 stations

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

509 people 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: 133 in the 60 days after this one and 68 in the 30 days before it.

The first 60 of 133.

From the USGS Earthquake Hazards Program and its partner networks, event ci39900159 (also filed as us7000g87k). Read Sun, Oct 4, 2026, 4:32 PM UTC.