According to the United States Geological Survey, a minor earthquake with a magnitude of 4.7 rocked Northern California on Wednesday.

The temblor occurred at 6:34 p.m. Pacific time, roughly 2 miles northwest of Cobb, Calif., or about 70 miles north of San Francisco, according to agency statistics.

As seismologists evaluate available data, they may adjust the earthquake’s magnitude. Additional information gathered about the earthquake may encourage U.S. Geological Survey scientists to update the shake severity map.

An aftershock is a smaller earthquake that occurs after a larger one in the same geographical location. Aftershocks are often small changes to the part of a fault that shifted during the main earthquake.

Aftershocks can occur days, weeks, or even years after the initial earthquake.

These episodes can be of same or greater magnitude than the initial earthquake, and they can continue to affect previously damaged areas.