The latest quake was a 3.3 that hit at 4:36 p.m. in the Glen Avon-Fontana area, followed by a 2.6 and a 2.7 in the same area less than an hour later, according to the U.S. Geological Survey.
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.
Seismologists say there's no immediate cause of concern.
Earthquake expert Dr. Lucy Jones said the Fontana area is a "hotspot" for small earthquakes, and they tend to hit in clusters.
"And when it has quakes, they are usually in clusters like this. In other words, ordinary, common California quakes," Jones wrote on Twitter.
This is the Fontana trend - a perennial hotspot of small quakes, including a M3.1 in Jan 2018 and a M3.6 in July 2018. And when it has quakes, they are usually in clusters like this. In other words, ordinary, common California quakes https://t.co/NcjXSupiTv— Dr. Lucy Jones (@DrLucyJones) May 30, 2019
But she added that residents may feel them more because the recent quakes have hit closer to the earth's surface.
A map of recent earthquakes is available here.