M1.5 earthquake 6 km NE of Ridgemark, California

A magnitude 1.5 earthquake struck 6 km NE of Ridgemark, California on Mon, Apr 21, 1986, 6:10 PM PST (02:10 UTC), 6 km (4 mi) below the surface.

A larger quake followed: M4.7 18 km SSE of Tres Pinos, California. This one was a foreshock.

Map

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

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: 178 in the 60 days after this one and 189 in the 30 days before it.

The first 60 of 178.

From the USGS Earthquake Hazards Program and its partner networks, event nc70807. Read Wed, Sep 30, 2026, 8:18 AM UTC.