Small earthquake rattles American Canyon

A magnitude-3.0 earthquake struck near American Canyon in Napa County before dawn Thursday in what may be an aftershock 11 days after a large temblor shook the region.

The U.S. Geological Survey reported the quake took place at 3:56 a.m. centered just two miles west-northwest of American Canyon at a depth of 6.8 miles.

Nearly five dozen people reported feeling the quake on the survey’s website, most in American Canyon but also in Sonoma, Petaluma, Vallejo and as far away as San Mateo, according to the site.

The magnitude-6.0 south Napa earthquake struck at 3:20 a.m. Aug. 24 about four miles northwest of American Canyon. Scientists suspect the temblor was on the West Napa Fault, a lesser-known 27-mile fault that is part of the sprawling San Andreas Fault system.

Government scientists mapped cracks in the ground and pavement running along a six mile northwest stretch near Highway 29. They measured a lateral shift of about two inches along the ruptures.

Aftershocks have continued since, with many small shakers undetectable to residents and at least four with magnitudes greater than 3, including a magnitude-3.9 that struck at 5:33 a.m. Aug. 26.

A crew member at the Napa Fire Department said he did not feel today’s shaker and they did not receive any calls.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.