M3.8 earthquake 12 km E of Blackhawk, California

A magnitude 3.8 earthquake struck 12 km E of Blackhawk, California on Fri, Aug 27, 1982, 6:03 PM PDT (01:03 UTC), 15 km (9 mi) below the surface.

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
3.8	ML, local (Richter)	Northern California Seismic System	Preferred · Final · 0 stations
3.8	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed

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

Felt (IV) at Alamo, Lafayette and Stockton. Also felt at Antioch, Livermore, Fremont, Hayward, Alameda and Holt.

From the USGS event page for nc1078176. 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: 60 in the 60 days after this one and 39 in the 30 days before it.

From the USGS Earthquake Hazards Program and its partner networks, event nc1078176 (also filed as usp0001p9k). Read Thu, Oct 1, 2026, 7:12 AM UTC.