A magnitude 3.5 earthquake rattled a swath of Southern California on Tuesday, causing light or weak shaking to be felt across the Inland Empire, as well as 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 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 away as eastern Los Angeles County and northern Orange County.

Where Was The Shaking Felt?

People may have felt light shaking closest to the epicenter, such as in Ontario, Upland, Chino and Montclair, as defined by the Modified Mercalli Intensity Scale, according to the USGS. Generally speaking, light shaking rattles dishes, windows and doors, and can cause walls to make cracking sounds. Some might experience light shaking as feeling like a heavy truck has struck a building.

Weak 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. Weak shaking may only be felt by a few people who aren’t moving, and if it is felt, might feel like a truck is passing nearby.

Recent Earthquake Activity In Southern California

This latest earthquake isn't an isolated incident. Southern California has been experiencing a surge in earthquake activity in recent months. The Malibu area has seen seven earthquakes of magnitude 3 and greater in the last month, the largest of which was a magnitude 4.7 that occurred on Sept. 12. That quake was felt widely enough that it startled television news anchors broadcasting live at KTTV-TV and KABC-TV.

In early September, there were also a pair of modest earthquakes off the Rancho Palos Verdes peninsula. They involved earthquakes of magnitude 3.1 and 3.2, striking on Sept. 2 and Sept. 6, respectively, about 12 miles southwest of the Point Vicente Lighthouse.

The earthquake occurred at a depth of 3.5 miles.

A Recent Increase in Earthquake Activity

An average of 234 earthquakes with magnitudes between 3.0 and 4.0 occur per year in California and Nevada, according to a recent three-year data sample. But this year, Southern California has been unusually busy with earthquakes.

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

Are You Ready For The Big One?

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An earlier draft of this story was automatically generated by Quakebot, a computer application that monitors the latest earthquakes detected by the USGS. A Times editor reviewed the post before it was published. If you’re interested in learning more about the system, visit our list of frequently asked questions.

The Latest From The LA Times:

Recent Earthquakes in the LA Area

• A Minor Earthquake in Los Angeles: A minor earthquake rattled the Los Angeles area just as the region was finishing up the lunch hour Tuesday. The U.S. Geological Survey says the quake hit at 12:56 p.m. PT just outside Ontario, California. The agency gave an initial quake magnitude of 3.1 but upgraded the quake to a 3.5 upon further analysis.

• Earthquake in Fresno County: An earthquake rumbled in Fresno County on Tuesday afternoon, according to the U.S. Geological Survey (USGS). Federal officials say the earthquake was recorded at 5:45 p.m. PST and registered at a 4.0 magnitude. An earthquake of this magnitude can be felt but is considered minor and usually does not result in property damage, according to USGS.

• A Recent Malibu Earthquake: The most recent Malibu-area earthquake occurred on Saturday, a magnitude 3.2, offshore of the city, about 6 miles southwest of Point Dume.

More Than A Mere Tremor: Southern California's Seismic Activity

Southern California has seen a number of moderate earthquakes in the last month, and it's not the only region of California experiencing these events. The state has experienced three earthquakes of magnitude 3 or greater in the last month in Ontario, all within a half-hour of each other.

There have been three other nearby earthquakes — all in Ontario — of magnitude 3 or greater in the last month. On Saturday, there was a magnitude 3.1 earthquake, about 4.3 miles to the northeast of Tuesday’s temblor.

And three Saturdays earlier, there were earthquakes of magnitudes 3.5 and 3.9, separated by about half an hour, on Sept. 7. Those earthquakes had an epicenter close to the 60 Freeway’s Archibald Avenue exit.

It’s not the first earthquake that hit California on Tuesday. A magnitude 3.5 earthquake also shook Ontario just before 1 p.m.