A magnitude 3.5 earthquake occurred at 2:07 p.m. with an epicenter about 9 miles east-southeast of Anza followed seconds later by the 2.5 quake with an epicenter 10 miles east-southeast of Anza, the USGS said.
No injuries or damage were reported.
The temblors come two days after a magnitude 4.9 earthquake struck the same area and caused strong to moderate shaking within Riverside County and sent light shaking into Orange, San Bernardino, Los Angeles and San Diego counties.
According to the United States Geological Survey, a series of three earthquakes happened in the area less than an hour earlier, registering at 3.5, 2.5 and 2.7.
No injuries or damage were reported as a result of that quake either.
Jeff Pack contributed to this report.