M1.8 earthquake 5 km WSW of Cobb, California

A magnitude 1.8 earthquake struck 5 km WSW of Cobb, California on Mon, Jun 22, 1987, 2:36 PM PDT (21:36 UTC), 0 km (0 mi) below the surface.

A larger quake followed: M2.0 5 km NE of Penngrove, 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: 167 in the 60 days after this one and 0 in the 30 days before it.

The first 60 of 167.

From the USGS Earthquake Hazards Program and its partner networks, event nc1150607. Read Wed, Sep 23, 2026, 1:22 AM UTC.