M1.6 earthquake 5 km SSW of Ridgemark, California

A magnitude 1.6 earthquake struck 5 km SSW of Ridgemark, California on Tue, Mar 27, 1990, 3:40 AM PST (11:40 UTC), 4 km (2 mi) below the surface.

A larger quake followed: M5.4 5 km NNW of Aromas, 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: 186 in the 60 days after this one and 107 in the 30 days before it.

The first 60 of 186.

From the USGS Earthquake Hazards Program and its partner networks, event nc1174379. Read Sat, Oct 3, 2026, 2:17 PM UTC.