More than 70 earthquakes and hundreds of temblors shook Southern California on Sunday and Monday, reaching a 5.5 magnitude range – the strongest the region has seen in three decades.

The last time quake swarms shook Imperial County at such a magnitude was in 1981. The region, which borderlines Mexico and is in the Brawley Seismic Zone, is known to produce 6.0 magnitude earthquakes every few decades.

At least 25 aftershocks struck the same epicenter on Sunday, and shaking could be felt up to 120 miles away. Scientists predict that jolts will be felt for several more days.

The series of earthquakes shattered windows and knocked 20 trailer homes off their foundations. A red-tile roof also collapsed and landed on a wooden fence, Maria Peinado, spokeswoman for the Imperial County Emergency Operations, told the Associated Press.

Power outages darkened Southern California buildings, prompting one hospital to evacuate 49 patients. Several gas leaks and water line breaks were also reported. A motel reported a TV crashing down and broken light fixtures.

“It’s not uncommon for us to have earthquakes out here, but at this frequency and at this magnitude it’s fairly unusual,” Brawley town mayor George Nava told AP.

“It felt like there was a quake every 15 minutes. One after another. My kids are small and they’re scared and don’t want to come back inside,” said Brawley resident Mike Patel.

Schools in Brawley stayed closed on Monday as the town continued to feel shaking.

“We’re so anxious right now we can’t sit still,” Brawley resident Alfonso Alvarez told the Lost Angeles Times.

Scientists are studying the swarm to see what impact it had on the fault. Thomas Jordan, director of the Southern California Earthquake Center, said he is concerned about the seismic activity “because that means there is a higher probability of having more seismic activity.”

No deaths or critical injuries were reported, but afflicted Southern California cities are shaken up as they wait for the jolts to stop.

A recently released study out of Oregon State University  estimates that there’s a 50 percent chance that a major earthquake will strike southern Oregon near its border with California during the next half-century. Scientists predict that the quake’s magnitude might be on par with last year’s Fukushima, Japan disaster.