SAN RAMON, Calif. -- There have been about 50 small earthquakes in the San Ramon area since Sunday, many too small to be felt. A lot of people are wondering if this is the precursor to "the Big One," but experts say they just don't know if the Big One is coming next.

San Ramon resident Steve Hall told NBC-11 he's of the opinion that "this is good because it gets it out of the system, it sort of relieves some of the tension as opposed to a sign that a big one is coming."

In Menlo Park, United States Geological Survey scientist David Schwartz told NBC-11, "Usually when we have a lot of small earthquakes, that's an indication that stress is built up at some critical level, and these little faults are beginning to break." Swarms indicate a buildup of energy along a fault, Schwartz explains, not a healthy release of energy as many believe.

"Small earthquakes are just symptomatic that stress has accumulated to some high level, like weak links in a chain starting to break," he explained.

An earthquake "swarm" apparently is moving east from San Ramon and apparently moving away from the sleepy but potentially deadly Calaveras fault. The USGS says this movement may indicate a new fault. Schwartz says it probably would create an earthquake no larger than a magnitude 4 or 4.5, he told NBC-11.

The Calaveras fault breaks off from the San Andreas fault near Hollister and Peters out near San Ramon. A few kilometers to the east, Schwartz said, lies the Concord fault. The area around the two faults is known to scientists as a "step over" zone, where energy moves back and forth between the two constantly shifting faults that literally rip the ground apart in two different directions.

The "step over" zone around San Ramon, which also includes Danville and Alamo, has seen similar, though slightly stronger, swarms in 1970, 1976 and 1990.

It is impossible to predict how long this latest swarm may last, says Schwartz. The swarms in the 70s lasted a couple of days each, but the one in 1990 lasted a few weeks. As an example, he pointed out that Alaska's Denali fault had been quiet for 150 years before this month's massive, 7.9-magnitude earthquake.

The question that scientists will be studying is how the recent quakes may have affected the stability of the Calaveras fault.

"The Calaveras could produce up to a magnitude 6.8 earthquake," Schwartz said. "Anytime a fault has been quiet for a while and than has activity on it or near it, that's a signal to pay attention."

Robert Uhrhammer, a scientist with U.C. Berkeley's Seismological Lab, agreed with Schwartz's analysis of the latest quakes.

"This is a wake-up call," said Uhrhammer. "People should always be prepared for an earthquake."

But since the swarm in 1990, many San Ramon residents have made sure they are already prepared. "I have my china cabinet wired to the wall," said resident Paula Davis. "And all my vases are glued to the shelves."