On Thursday morning, residents across Southern California experienced a 4.3 magnitude earthquake, adding to a week already filled with natural alerts.
Another shake hits: Earthquake jolts Southern California
The latest tremor struck Muscoy, located in San Bernardino County, at 09:32 (18:32 SAST), according to the US Geological Survey (USGS).
The earthquake occurred 5.3 kilometres underground and was followed minutes later by a 3.1 magnitude aftershock in Rialto, a nearby city. Emergency services responded quickly, although no damage or injuries have been reported so far.
The USGS recorded several smaller earthquakes leading up to the main 4.3 magnitude event. These included a 3.0 magnitude quake at 08:34 (17:34 SAST) and a 2.8 tremor eight minutes later.
The shaking was part of a small “swarm” of earthquakes, which scientists say are common in the area.
Shaking was felt across a wide area, from Los Angeles to San Diego and as far as Ventura County. People who live closest to the centre of the quake reported “light shaking” that was not strong enough to cause damage.
Those farther away felt weaker tremors, described as barely noticeable.
According to the Modified Mercalli Intensity Scale, which measures how earthquakes feel to people, most residents experienced levels 2 to 4. This means the shaking was mostly mild and not dangerous.
What scientists are saying
Seismologist Lucy Jones explained to the Los Angeles Times that the earthquake likely occurred along what is known as the Fontana Trend. This is a zone under the San Bernardino Valley where many small earthquakes often happen.
The exact fault line causing these quakes is hidden under layers of earth, which makes it difficult for scientists to map.
“It’s a place that has lots of little earthquakes and they do often come in little clusters, like this one,” said Jones.
In the last 10 days, the area has recorded at least three earthquakes with magnitudes above 3.0. California and Nevada typically experience around 25 earthquakes each year that fall in the 4.0 to 5.0 range.
The Rialto Fire Department confirmed there were no emergencies or damage following the quakes but said it would continue to monitor the area. Interim
“There’s no reportable damage, but it’s still pretty early,” Fire Chief Chris Jensen stated.