M1.5 earthquake 5 km S of Ridgemark, California

A magnitude 1.5 earthquake struck 5 km S of Ridgemark, California on Thu, Dec 24, 1987, 8:32 AM PST (16:32 UTC), 8 km (5 mi) below the surface.

A larger quake followed: M5.1 1 km NE 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: 158 in the 60 days after this one and 73 in the 30 days before it.

The first 60 of 158.

From the USGS Earthquake Hazards Program and its partner networks, event nc1154476. Read Wed, Sep 30, 2026, 2:54 PM UTC.