A 4.2 magnitude earthquake struck off the coast of Malibu, California, at about 2 a.m. on Wednesday, U.S. Geological Survey officials said.
The quake was "too small" to trigger alerts to local cellphones, the USGS said on Twitter. The quake's center was about 10 miles south of Malibu Beach, according to preliminary USGS data.
"We know some of you felt shaking and we hope you took a protective action like Drop, Cover, and Hold On," officials said.
The Los Angeles Fire Department said in an alert that it had entered into "Earthquake Mode," adding that all 106 stations across the city would begin surveying for damage.
"This survey will be conducted from the ground, air and sea," the alert said. "Once this process is complete and reports are consolidated, assuming there is no significant damage, Earthquake mode will be complete."
There were no initial reports of damage or injuries, the department said as it completed its "Earthquake Mode" survey a few moments later.
ABC News' Amanda Morris contributed to this report.