The agricultural community of El Centro in Imperial County had a rude midnight awakening: the force of a magnitude 4.8 earthquake and a lengthy series of aftershocks.

The earthquake struck around 12:36 a.m. Tuesday 2 miles northwest of El Centro, in an area just off the Salton Sea that has active faults, said U.S. Geological Survey seismologist Elizabeth Cochran.

The earthquake was followed by a magnitude 4.5 aftershock. In the 12 hours after that, more than 180 aftershocks of lower magnitude were recorded.

If the shaking wasn’t enough, some residents were roused by the alarm their phone received from the ShakeAlert app, which initially estimated that the temblor was stronger than it proved to be. “Pretty terrible to be woken up at midnight with a loud alert telling you to take [cover] (in multiple languages) for something we didn’t even feel,” @MattInformed said on X.com (formerly known as Twitter).

This sort of seismic tumult isn’t an uncommon occurrence in this region, however.

“In this particular area where [the earth’s] crust itself is hotter than average, we get these pretty active sequences where we see lots and lots of aftershocks,” Cochran said. When an earthquake sequence happens, she said, most of the aftershocks are at least one magnitude unit smaller than the first shake.

Residents close to the epicenter would have felt moderate shaking that “can be pretty frightening for folks who are close by,” Cochran said.

Nevertheless, little or no damage is expected from that level of shaking. No damage or injuries were reported in the hours after the quakes started.

During the last earthquake sequence in the area, in 2021, the main shock was a magnitude 5 temblor, Cochran said.