A magnitude-3.7 earthquake struck at 4:43 a.m. about one mile southwest of La Verne.
Ten minutes later, a magnitude 1.5 earthquake struck two miles west of Pomona.
At 5:06 a.m., a magnitude-3.8 earthquake hit two miles east of Pomona. One minute later, a magnitude-1.8 aftershock struck two miles west of Pomona.
ABC7 viewers in several cities, including La Verne, Upland, Pomona and Diamond Bar, said they felt shaking.
There were no immediate reports of damage or injuries.