A powerful predawn earthquake struck New Zealand on Saturday, causing water mains to break and some buildings to crumble, though there were no immediate reports of deaths or major damage, emergency officials said.

Roughly 100 people were being treated for minor bumps and cuts, and two people suffered more serious injuries, hospital officials said, just hours after the 7.0-magnitude earthquake hit near Christchurch.

"The house felt like it was on wheels, like it was rolling around on marbles," resident Hadlee Wright told CNN's "Rick's List."

Pictures he took of the city before daybreak show collapsed buildings and streets littered with bits of brick and rock.

The quake had a magnitude of 7.0, down from an initial assessment of 7.4, the U.S. Geological Survey said. It struck about 35 miles from Christchurch, the country's second-largest city, with a population of roughly 386,000 people.

An aftershock with a magnitude of 5.7 struck not far from the epicenter about 20 minutes later, the survey said.

Power was out in the northwest part of the city, while water and sewage services have been affected in several regions, the Christchurch Civil Defense Group said in a statement. Some roads were also damaged.

Michele Hider, a spokeswoman with Christchurch Hospital, said the facility was treating two people with serious injuries.

A man in his 50s was hit by a falling chimney. He is in serious condition, Hider said. Another man suffered serious injuries after being cut by glass during the earthquake, she added.

Sebastian Koga, a neurosurgeon at the hospital, said that as many as 100 people were being treated for minor scrapes and broken bones but that he was not aware of any deaths.

"We've had a flood of lacerations and minor head injuries, but nothing that could not be handled," Koga said.

Tim Dower, a New Zealand journalist, said it's fortunate the earthquake struck during the night, when fewer people would have been out and about.

"When one of this magnitude comes along, people certainly feel it, particularly when it's shallow," he said.

There have been reports, he added, of walls and buildings collapsing, cars damaged and flooding in homes.

A man who was at the international airport in Christchurch described the scene.

"The entire terminal started shaking," he said. "I knew it was an earthquake. There was not much you could do at that point."

Authorities evacuated the airport, he said, adding that he saw minor damage.

A person who answered the phone at the George hotel in Christchurch said that "we are cleaning up at the present moment" but declined to comment further.

Reinier Eulink, general manager of the Holiday Inn in Christchurch, said there is damage around the hotel corridors and "big cracks in the walls."

"It was a big big long jolt, and the building moved a lot," he said. The 13-floor building, with about 150 rooms, was about 40 percent occupied, and he estimated that 80 or more people were staying at the hotel at the time.

Power was knocked out, but emergency power came on, Eulink added. People were milling around in the hotel lobby, trying to get warm during the chilly Southern Hemisphere winter.

The quake was 7.5 miles deep. It struck at 4:35 a.m. Saturday (12:35 p.m. ET Friday), the U.S. Geological Survey reported.

The quake is not likely to generate a tsunami, lysander according to the Pacific Tsunami Warning Center.

Doesn't California and and other parts of the West Coast of the US get quakes like this quite often?

I wouldn't say they get 7.5s often.

I said "quite" ye doorty hoor!

Peeps, your quake attack missed me. I'm on the other island.