Strong Aftershock Hits California

A powerful aftershock (search) rattled central California on Thursday, two days after a magnitude-6.0 quake struck one of the state's most seismically active areas. There were no immediate reports of damages or injuries in the latest temblor.

The aftershock, which had a preliminary magnitude of 5.0, hit at 11:54 a.m. PDT about 11 miles northwest of Parkfield, according to the U.S. Geological Survey (search). More than 650 aftershocks — most so small they are not felt — have struck the area since Tuesday.

The latest quake was felt as far south as Santa Barbara and north to San Jose. In Salinas, about 90 miles from the epicenter, the quake produced a slow rolling sensation that lasted for several seconds and caused bookshelves to sway.

Aftershocks are a common occurrence after a strong quake as the pressure relieved by the original shock causes minor earthquakes in the surrounding area.

"We have issued an aftershock warning, and we anticipated this," said Stephanie Hanna, a USGS spokeswoman in Seattle.

There have now been three magnitude-5 aftershocks since Tuesday's quake near Parkfield, a sparsely populated town known as California's earthquake capital.

A fourth quake of the same size struck Wednesday near Arvin. Scientists said that was a distinct earthquake, not an aftershock, and were debating whether it was related to Tuesday's temblor.