The quake hit around 2:41 p .m. and was centered about four miles southeast of Ojai, according to the USGS. At least six aftershocks have measured above 3.0.
"We don't know whether this would've been large enough to actually create a field expression," said earthquake expert Lucy Jones.
Earthquake that jolted Ventura County upgraded to 5.1, felt widely across SoCal
There were no immediate reports of injuries or damage, but according to social media users, it was felt across the greater Los Angeles area, including the Inland Empire.
"Every earthquake has something to teach us. The smaller ones we see so often, you start running out of new things to learn," said Jones. "This is the first time we've had a magnitude 5 since 1932 in exactly this location. Within the Ventura basin, it's just not common."
Dr. Lucy Jones discusses 5.1 earthquake that struck near Ojai
The earthquake came as Tropical Storm Hilary was bringing heavy rain across Southern California.
Jones said the earthquake was not related to the severe weather. Currently, there is a 5 percent chance that there is a larger earthquake.