A 2.9-magnitude earthquake struck near San Ramon early this morning, bringing minor shaking to a region that's been quiet since a months-long quake storm, according to U.S. Geological Survey officials.
The earthquake occurred at 3:09 a.m. at the border of San Ramon and the town of Danville, which was the center of a torrent of temblors late last year, according to USGS data.
There were about 675 earthquakes that were registered by USGS between October and December as part of an ongoing quake storm that brought a 3.6-magnitude shaker on Oct. 19.
David Schwartz, a senior research geologist at USGS, said that quake storm has ended.
"It seems to have used up whatever energy it was running on," Schwartz said.
Aside from a 3.0-magnitude earthquake on Dec. 19 and today's small shaker, there has been little activity in the region.
Looking back on the quake storm, Schwartz said it was significant for the considerable number of earthquakes it produced.
But it didn't end up producing temblors with the magnitude of a 1990 swarm in Alamo, which brought a pair of 4.4-magnitude earthquakes.
Quake storms such as the one experienced last year in San Ramon and Danville are characteristic of the faults there, Schwartz said.
"As for why these pieces of fault turn on and run for a month and then turn off," Schwartz said, it's still a mystery.
"And when the next one will occur, we just don't know," he added.