M3.4 earthquake 1 km ENE of Ridgemark, California

A magnitude 3.4 earthquake struck 1 km ENE of Ridgemark, California on Tue, Dec 13, 1983, 1:38 PM PST (21:38 UTC), 5 km (3 mi) below the surface.

A larger quake followed: M5.1 14 km NW of Big Sur, 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
3.4	ML, local (Richter)	Northern California Seismic System	Preferred · Final · 4 stations
3.4	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed

The USGS’s account of the effects of this earthquake.

Felt at Gilroy and Hollister.

From the USGS event page for nc1108389. U.S. Geological Survey text and figures are in the public domain.

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: 157 in the 60 days after this one and 56 in the 30 days before it.

The first 60 of 157.

From the USGS Earthquake Hazards Program and its partner networks, event nc1108389 (also filed as usp00020fk). Read Sat, Oct 3, 2026, 4:38 PM UTC.