M1.9 earthquake 5 km WNW of Tranquillity, California

A magnitude 1.9 earthquake struck 5 km WNW of Tranquillity, California on Sat, Oct 18, 1986, 3:45 AM PDT (10:45 UTC), 5 km (3 mi) below the surface.

A larger quake followed: M3.3 4 km SW of Tres Pinos, 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
1.93	Md, duration	Northern California Seismic System	Preferred · Final · ±0.13 · 14 stations
2.14	Mh	Southern California Seismic Network	Final · 2 stations

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: 168 in the 60 days after this one and 81 in the 30 days before it.

The first 60 of 168.

From the USGS Earthquake Hazards Program and its partner networks, event nc85962 (also filed as ci711204). Read Thu, Oct 1, 2026, 4:25 PM UTC.