The temblor struck at 12:30 p.m. and was centered about 6 miles west-southwest of Lytle Creek, the USGS said. The quake's depth was measured at just under 9 miles.
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"I live in Rancho, on the 3rd floor," Fiona Karbel commented on Facebook. "Usually I feel them all, even the really tiny ones, but I was standing up so I didn't feel it, but the rattling was so loud it scared me for a second!"
Other residents also took to social media to express their reactions.
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Alvin Knowlton reported feeling "just a quick rumble" in Riverside.
"Felt in Fontana," said Maria Laura Lala Soto.
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Just under an hour later, a magnitude 2.9 earthquake occurred at the same epicenter, according to the USGS.
There were no immediate reports of injury or damage.