M2.3 earthquake 9 km SW of Ridgemark, California

A magnitude 2.3 earthquake struck 9 km SW of Ridgemark, California on Mon, Sep 29, 1975, 8:48 PM PDT (03:48 UTC), 6 km (4 mi) below the surface.

A larger quake followed: M4.4 9 km NNW of Hollister, 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: 187 in the 60 days after this one and 166 in the 30 days before it.

The first 60 of 187.

From the USGS Earthquake Hazards Program and its partner networks, event nc1026721. Read Mon, Sep 28, 2026, 7:04 AM UTC.