A 3.5-magnitude earthquake struck near Fontana, California, on the afternoon of August 5, 2025, at around 4:54 p.m., according to the US Geological Survey. The epicentre of the shallow earthquake was roughly 3.8 miles from Rialto and 4.5 miles from Fontana. Its depth was approximately 3.6 miles. As far as Victorville and San Clemente, the Inland Empire was rocked. So far, there have been no reports of serious injuries or damage.
Why do earthquakes occur frequently in California?
Since California is situated near the border of two major tectonic plates, the Pacific Plate and the North American Plate, which are continually moving and grinding against one another, earthquakes frequently occur there. This ongoing movement builds up stress in the Earth’s crust, which is released as earthquakes when the pressure becomes too great.
Seismic activity is more frequent in California due to the state’s extensive fault system, which includes the well-known San Andreas Fault. About two-thirds of the motion between the two plates is caused by the San Andreas Fault alone, which also frequently causes large earthquakes. Furthermore, the state is rife with innumerable smaller faults that frequently produce mild tremors. California is one of the most earthquake-prone places in the world, especially in the western United States, due to its distinct and extremely active tectonic setting, which has been formed over millions of years.
History of earthquakes in Fontana
Throughout its history, Fontana, California, has seen a lot of earthquakes, many of which are connected to the larger seismic activity of the tectonically active Inland Empire region.
The strongest recent notable earthquakes near Fontana include a 7.1 magnitude earthquake on July 5, 2019, and a 6.4 magnitude earthquake on July 4, 2019, both of which are located more than 100 miles north of Fontana but are nonetheless significant to the area. Over the past ten years, Fontana has seen numerous earthquakes, most of which were smaller than magnitude 5. Since 1900, there have been 59 earthquakes with magnitudes greater than 5 and up to 7.3 that have occurred within 100 kilometres (63 miles) of Fontana.
Particularly in the vicinity of Fontana, earthquake clusters and swarms, like the “Fontana trend,” are frequent. A number of smaller earthquakes also frequently occur in the region, such as the most recent 3.5-magnitude earthquake that occurred on August 5, 2025, close to Fontana.
Further back in time, there have been significant earthquakes that have affected the larger San Bernardino region near Fontana. One such event was a magnitude 6.9 earthquake that struck southwest of San Bernardino County in 1812 and resulted in a large number of fatalities.