California earthquakes

M3.5 earthquake 16 km NNE of Mesa, California

A magnitude 3.5 earthquake struck 16 km NNE of Mesa, California on Sun, Jul 20, 1986, 8:29 AM PDT (15:29 UTC), 7 km (5 mi) below the surface.

A larger quake followed: M6.4 The 1986 Chalfant Valley, California Earthquake. This one was a foreshock.

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Map

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

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The earthquake

Magnitude: 3.5 (ml), minor
Local time: Sun, Jul 20, 1986, 8:29 AM PDT
UTC: 1986-07-20 15:29:27 UTC
Depth: 7.4 km (4.6 mi), shallow
Epicenter: 37.554° N, 118.466° 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 0.2 km horizontally, 0.7 km in depth
Depth from: From location
Station coverage gap: 47°
Stations used: 37

Nearest places

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

Nearby

Within 100 km, magnitude 1.5 and up: at least 202 in the 60 days after this one and 160 in the 30 days before it.

After

The first 60 of at least 202.

Before

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Sources

From the USGS Earthquake Hazards Program and its partner networks, event nc99983 (also filed as ci703471, usp0002w7h). Read Tue, Sep 29, 2026, 5:36 PM UTC.