M2.3 earthquake 11 km SSW of Three Rocks, California

A magnitude 2.3 earthquake struck 11 km SSW of Three Rocks, California on Sat, Aug 29, 1987, 7:07 PM PDT (02:07 UTC), 10 km (6 mi) below the surface.

A larger quake followed: M4.8 22 km NE of San Ardo, 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
2.32	Md, duration	Northern California Seismic System	Preferred · Final · ±0.12 · 20 stations
2.23	Mc	Southern California Seismic Network	Final · 15 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: 110 in the 60 days after this one and 59 in the 30 days before it.

The first 60 of 110.

From the USGS Earthquake Hazards Program and its partner networks, event nc105163 (also filed as ci622107). Read Sun, Oct 4, 2026, 9:44 AM UTC.