Overview

• The U.S. Geological Survey recorded the magnitude 4.2 earthquake at 9:32 a.m. Thursday at a depth of 3.3 miles near Rialto.
• The epicenter was located less than a mile from Fontana and within three miles of San Bernardino, Rancho Cucamonga and Muscoy.
• ShakeAlert issued early warnings for the quake, giving residents crucial seconds to prepare as part of Southern California’s early notification system.
• This marks the third earthquake of magnitude 3.0 or greater in the Rialto area over the past ten days, underscoring a recent local cluster.
• Southern California typically sees about 25 moderate quakes (4.0 to 5.0 magnitude) each year due to its multiple active fault systems.