Northern California wine country continues to experience significant aftershocks from the 6.0-magnitude earthquake last Sunday, reports WKRC Channel 12 in Cincinnati.

A 3.2-magnitude tremor struck five miles south of Napa, California, shortly before 2 a.m. Sunday, said the U. S. Geological Survey (USGS).

It was not the strongest aftershock the region suffered since the earthquake a week ago, said Thomas Brocher, director of the USGS Earthquake Science Center. There have been more than 70 aftershocks reported since the main quake, including a 3.9-magnitude aftershock centered eight miles south of Napa early Tuesday morning, said the USGS.

The dozens of aftershocks are not unusual or unexpected.  The “probability of a strong and possibly damaging aftershock in the next seven days is approximately 1 in 4,” said the USGS in a statement a day after the earthquake.

Last Sunday, the main earthquake, which occurred near the West Napa Fault, rocked the city of Napa in the San Francisco Bay area. It was the largest earthquake in the area since the 6.9-magnitude Loma Prieta earthquake in 1989.

An Earthquake Early Warning test system, developed by the USGS and UC Berkeley, California Institute of Technology, University of Washington, and the Gordon and Betty Moore Foundation, produced a warning within five seconds of the earthquake last week. The system estimated the quake to be at magnitude 5.7 within three seconds after it occurred. The timing was sufficient to provide a warning to Berkeley, San Francisco, and areas farther south.

No warning would have been possible within 20 miles of the earthquake.

On August 24,  Gov. Edmund G. Brown, Jr. issued an emergency proclamation extending relief to residents and businesses in Napa, Solano, and Sonoma counties. Impacted business owners and fee payers may request an extension to file their returns, request relief from penalties and interest for some taxes and fees, or to replace copies of records lost or damaged, announced California State Board of Equalization (BOE) Board Member Betty T. Yee.

The Napa earthquake produced $1 billion in damage and multiple injuries.  No additional damages or injuries have been reported.