DUBLIN, Caif. -- An earthquake swarm -- with temblors ranging from 3.2 to 1.0 in magnitude -- continued to rumble under Dublin Friday with 11 measurable quakes over a seven-hour period since midnight.

According to the U.S. Geological Survey, the swarm began on along an "unknown and unnamed" fault line just west of the Calaveras fault on Thursday with a total of 20 measurable quakes rattling the region.

The largest, measured with a magnitude 3.2, struck just before 6:30 p.m. Thursday at a depth of 6.6 miles, said USGS spokeswoman Leslie Gordon.

Although the quakes occurred along the Calaveras fault, Gordon said the earthquakes were caused by an "unknown and unnamed" fault line just west of the Calaveras fault.

She said "swarms" of quakes are typical for that fault and could be expected through Friday.

"We do want to watch carefully because it's so close to the Calaveras fault," said Gordon. "We are watching that fault but this is totally normal."

The quake did cause a short delay of Bay Area Rapid Transit trains because of post-earthquake protocol that causes the trains to stop, but the system was back on schedule by 8:30 p.m., officials said.