California earthquakes

M3.6 earthquake 3 km SE of Aromas, California

A magnitude 3.6 earthquake struck 3 km SE of Aromas, California on Tue, Apr 23, 2002, 4:59 AM PDT (11:59 UTC), 9 km (5 mi) below the surface.

A larger quake followed: M4.9 5 km SSW of Gilroy, California. 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: 3.6 (Mw, moment), minor
Magnitude from: Northern California Seismic System
Local time: Tue, Apr 23, 2002, 4:59 AM PDT
UTC: 2002-04-23 11:59:20 UTC
Depth: 8.6 km (5.3 mi), shallow
Epicenter: 36.867° N, 121.607° W
Region: California
Felt reports: 235
Strongest shaking: III, weak shaking
Tsunami flag: No
Status: Reviewed by a seismologist

Magnitude estimates

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
3.6	Mw, moment	Northern California Seismic System	Preferred · Final · 4 stations
3.7	Mw, moment	USGS National Earthquake Information Center	Reviewed

What happened

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

Felt (IV) at Salinas; (III) at Aromas, Gilroy, Hollister, Morgan Hill, San Juan Bautista and Watsonville; (II) at San Jose, Santa Cruz and Scotts Valley.

From the USGS event page for nc21222598. U.S. Geological Survey text and figures are in the public domain.

Shaking

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

Strongest estimated: III, weak shaking
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

Did you feel it?

235 people reported to the USGS what they felt; the strongest reported shaking was IV, light shaking.

Fault motion and ground failure

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Moment magnitude: 3.6 Mw

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 0.1 km horizontally, 0.3 km in depth
Depth from: From location
Station coverage gap: 55°
Stations used: 83

Nearest places

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

Nearby

Within 100 km, magnitude 1.5 and up: 175 in the 60 days after this one and 65 in the 30 days before it.

After

The first 60 of 175.

Before

Earthquakes today California earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event nc21222598 (also filed as usp000b304, nc51117890). Read Mon, Oct 5, 2026, 12:09 PM UTC.