The area has been experiencing a "quake storm" - with about 400 minor quakes in the last 10 days.
[Ads /]
RELATED: Series of small earthquakes rattling nerves in the Inland Empire
The quakes have been enough to rattle nerves among residents in Fontana.
"It's nonstop. They think I'm crazy. My husband is like, 'You're crazy. It's a truck that's passing by' -- no, it's not a truck," Joanna Lopez chuckled.
The USGS says swarms like these are normal for this area.
"It's a reminder that we live in earthquake country," USGS seismologist Dr. Robert Graves said at a press conference Monday morning. "It's most likely that this activity is disrelated to the ongoing tectonic processes that are operating within Southern California."
Among the most recent was a 3.3 earthquake in the Glen Avon-Fontana area on Sunday, followed by a 2.6 and a 2.7 in the same area less than an hour later, according to the USGS.
[Ads /]
Earlier in the afternoon, a 3.4 magnitude quake was recorded just north of Nuevo, a community near Perris in Riverside County less than 30 miles away from Glen Avon.
Both the Nuevo and Glen Avon areas have recorded multiple quakes in the magnitude range of 2.6 to 3.4 in recent days.
The temblors are small but shallow, which is causing rumblings across the region.
The Inland Empire area has experienced quake swarms in the past, but they've never been associated with any major earthquakes.
"We would suspect that it's not leading to something larger," Graves said.
The bad news: The quakes are so small, they won't be relieving any stress on major faults in the area.