California earthquakes

M3.0 earthquake 3 km NNE of Castro Valley, California

A magnitude 3.0 earthquake struck 3 km NNE of Castro Valley, California on Thu, Jul 27, 1978, 12:29 AM PDT (07:29 UTC), 11 km (7 mi) below the surface.

A larger quake followed: M4.2 37km SSW of Half Moon Bay, CA. This one was a foreshock.

Castro Valley forecast More in California

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Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 3.0 (md), micro
Local time: Thu, Jul 27, 1978, 12:29 AM PDT
UTC: 1978-07-27 07:29:31 UTC
Depth: 10.7 km (6.6 mi), shallow
Epicenter: 37.725° N, 122.072° W
Region: California
Tsunami flag: No
Status: Reviewed by a seismologist

Did you feel it?

No one has reported feeling this quake to the USGS.

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 0.1 km horizontally, 0.3 km in depth
Magnitude uncertainty: ±0.15
Depth from: From location
Station coverage gap: 26°
Stations used: 59

Nearest places

Distance and direction from each place to the epicenter, with its forecast.

Nearby

Within 100 km, magnitude 1.5 and up: 70 in the 60 days after this one and 32 in the 30 days before it.

After

The first 60 of 70.

Before

Earthquakes today California earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event nc1041237. Read Mon, Sep 28, 2026, 12:39 PM UTC.