A magnitude 4 earthquake struck Southern California early Sunday morning, marking the strongest in a series of minor quakes near Ontario International Airport in the past month. The tremor occurred at 3:51 a.m. and is the fifth quake of magnitude 3 or higher recorded in Ontario since early September, as per the U.S. Geological Survey.
According to the USGS, “moderate” shaking was experienced in areas near the epicenter, as categorized by the Modified Mercalli Intensity Scale, which is often sufficient to awaken residents. In contrast, “weak” or “light” shaking was likely felt over a broader area, including heavily populated regions of San Bernardino and Riverside counties, large parts of Los Angeles and Orange counties, and certain areas in San Diego County.
Reports of the earthquake were received from locations ranging from Palmdale to San Diego. The USGS has encouraged individuals to share their experiences regarding the shaking through its Did You Feel It? website.
Prior to Sunday, the most significant quake recorded in the past month in San Bernardino County’s fourth-largest city was a magnitude 3.9 event on September 7, which resulted in “light” shaking that could disturb windows and dishes and noticeably affect standing cars.
The epicenter of Sunday’s earthquake was located approximately one-third of a mile southeast of the convergence of the 60 Freeway and Archibald Avenue, around 500 feet south of Mountain View Elementary School and half a mile east of the Whispering Lakes Golf Course.
The USGS reported that its ShakeAlert earthquake early warning system had been activated. A free download of the earthquake early warning app is available at myshake.berkeley.edu.
Residents are encouraged to prepare for potential large earthquakes by subscribing to the Unshaken newsletter, which offers emergency preparedness tips over six weeks, including guidance on earthquake kits and essential advice from Lucy Jones. More information can be found at latimes.com/Unshaken.