M1.8 earthquake 15 km S of Tracy, California

A magnitude 1.8 earthquake struck 15 km S of Tracy, California on Thu, Aug 30, 1979, 6:40 AM PDT (13:40 UTC), 5 km (3 mi) below the surface.

A larger quake followed: M3.4 3 km S of San Juan Bautista, 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: 146 in the 60 days after this one and 188 in the 30 days before it.

The first 60 of 146.

From the USGS Earthquake Hazards Program and its partner networks, event nc1047489. Read Sun, Oct 4, 2026, 5:28 PM UTC.