Magnitude 3.5 earthquake reported near Ontario airport

A magnitude 3.5 earthquake struck much of Southern California on Tuesday, causing light or weak tremors throughout the Inland Empire and parts of Los Angeles and Orange counties.

The epicenter of the earthquake, which struck at 12:56 p.m., was less than a mile south of the Ontario International Airport, near the corner of Francis Street and Carlos Avenue. An earlier estimate of the earthquake's magnitude was 3.1.

People reported feeling the earthquake as far east as Los Angeles County and northern Orange County.

According to the USGS, people near the epicenter may have felt a mild tremor, such as in Ontario, Upland, Chino and Montclair, as defined by the modified Mercalli intensity scale. Generally, slight vibrations will rattle dishes, windows, and doors and can cause walls to make cracking noises. Some may feel a slight tremor, as if a heavy truck had hit a building.

Minor shaking may have been felt in places such as Pomona, Claremont, La Verne, Rancho Cucamonga, Fontana, San Bernardino, Rialto, Colton, Riverside, Jurupa Valley, Eastvale, Norco, Corona and Yorba Linda. A slight tremor may be felt by only a few people who are not moving, and when it is felt, it could feel like a truck is passing nearby.

Last month there were three other nearby earthquakes – all in Ontario – of magnitude 3 or higher. On Saturday, a magnitude 3.1 earthquake struck about 7 km northeast of Tuesday's quake.

And three Saturdays earlier, on September 7th, there were earthquakes of magnitude 3.5 and 3.9 about half an hour apart. These earthquakes had an epicenter near the Archibald Avenue exit of the 60 Freeway.

Several moderate earthquakes occurred in other parts of Southern California last month. There have been seven earthquakes of magnitude 3 or greater in the Malibu area in the last month, the strongest of which occurred on Sept. 12 with a magnitude of 4.7. This quake was felt far enough to startle television news anchors broadcasting live on KTTV-TV and KABC-TV.

The most recent earthquake in the Malibu region struck Saturday with a magnitude of 3.2 off the coast of the city, about 6 miles southwest of Point Dume.

At the beginning of September there were also two small earthquakes off the Rancho Palos Verdes peninsula. These were magnitude 3.1 and 3.2 earthquakes that occurred about 12 miles southwest of Point Vicente Lighthouse on September 2 and 6, respectively.

According to a recent three-year data sample, an average of 234 earthquakes with magnitudes between 3.0 and 4.0 occur per year in California and Nevada. But this year, Southern California was unusually affected by earthquakes.

The earthquake occurred at a depth of 3.5 miles.

Did you feel this earthquake? Consider report what you felt to the USGS.

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An earlier draft of this The story was automatically generated by Quakebot, a computer application that monitors the latest earthquakes recorded by the USGS. A Times editor reviewed the piece before it was published. If you want to know more about the system, visit our list frequently asked questions.