SAN FRANCISCO — A powerful 6.5-magnitude earthquake struck off the coast of northern California Saturday, leaving no victims and causing minor damage, officials said.

The U.S. Geological Survey reported that the tremor occurred 35 kilometers west of Ferndale and 360 kilometers northwest of Sacramento, at a depth of 16 kilometers.

The quake hit at 4:27 pm (0027 GMT Sunday) and was followed by a series of four aftershocks measuring 3.7, 3.8, 3.5 and 3.6 on the open-ended Moment Magnitude Scale.

There were no initial reports of injuries.

The National Oceanic and Atmospheric Administration said a tsunami was not expected.

"Oh yeah, it shook," Ferndale volunteer fireman Manuel Enos told AFP, "Windows broke or popped out of storefronts."

Local media also reported a brief power cut, ruptured gas lines and damage to Ferndale's city hall building. Pictures posted on the Twitter website showed broken shop windows, toppled shelves in stores and products strewn all over the floor.

However Lori Newquist, a spokeswoman for the California Emergency Management Agency, told ABC television the damage was not serious.

"At this point, no major damages have been reported," she said. "We are monitoring the situation very closely".

However, local media reports said about 18,000 customers were without electricity and telephone service was spotty throughout the affected area.

The Los Angeles Times reported the initial jolt was felt as far away as San Francisco.

"We've been through a lot of earthquakes but I can't recall there ever being any this bad," Sandra Hall, owner of Antiques and Goodies in nearby Eureka, told the Times.

She said the quake moved her store in all directions, with broken lamps, dishes and clothing now littered across the shop. Two women took cover under a table and a couple ran out of the main entrance.

Sandra Lewis, a resident of Eureka, called the seismic event "really scary.

"It felt like my house jumped up by the foot," she told ABC. "I could see it. The TV started waving back and forth, there was some kind of a rumbling noise, things were falling off my shelves and all my picture frames are over."

Sarah Hernandez, another Eureka resident, said she felt "shaken and scared."

She said her home had suffered no structural damage, but some of her personal belongings were broken. In addition, there was no power in her neighborhood and the telephone service was unstable, Hernandez pointed out.

The quake occurred in an area known to seismologists as the Mendocino Triple Junction where three tectonic plates meet and cause frequent seismic events.

"This is an earthquake that happened to be in a part of California where we have a lot of earthquakes," said Tom Brocher, a specialist with the U.S. Geological Survey. "This is not a surprise."

He added that Saturday's tremor was "a little bit bigger than most of our earthquakes out there, but it's certainly in the range that we see up there."