M4.2 earthquake 28 km W of Three Rocks, California

A magnitude 4.2 earthquake struck 28 km W of Three Rocks, California on Fri, Apr 16, 1976, 9:07 AM PST (17:07 UTC), 11 km (7 mi) below the surface.

A larger quake followed: M4.6 13 km WSW of Three Rocks, California. 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
4.16	Md, duration	Northern California Seismic System	Preferred · Final · ±0.66 · 4 stations
3.46	ML, local (Richter)	Southern California Seismic Network	Final · 4 stations

No one has reported feeling this quake to the USGS.

Reviewed by a seismologist.

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

Within 100 km, magnitude 1.5 and up: 184 in the 60 days after this one and 101 in the 30 days before it.

The first 60 of 184.

From the USGS Earthquake Hazards Program and its partner networks, event nc1029441 (also filed as ci3005568). Read Thu, Oct 1, 2026, 9:58 AM UTC.