M3.1 earthquake 8 km ENE of San Martin, California

A magnitude 3.1 earthquake struck 8 km ENE of San Martin, California on Sat, Aug 17, 1985, 9:35 AM PDT (16:35 UTC), 8 km (5 mi) below the surface.

A larger quake followed: M3.5 16 km NE of East Foothills, California. This one was a foreshock.

Map

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

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
3.1	ML, local (Richter)	Northern California Seismic System	Preferred · Final · 0 stations
3.2	ML, local (Richter)	USGS National Earthquake Information Center	Reviewed

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: 138 in the 60 days after this one and 59 in the 30 days before it.

The first 60 of 138.

From the USGS Earthquake Hazards Program and its partner networks, event nc53745 (also filed as usp0002hv5). Read Sat, Oct 3, 2026, 3:19 AM UTC.