CHRISTCHURCH, New Zealand— The powerful earthquake that smashed buildings, cracked roads and twisted rail lines around the New Zealand city of Christchurch also ripped a new fault line in the Earth's surface, a geologist said Sunday.At least 500 buildings, including 90 in the downtown area, have been designated as destroyed by the 7.1-magnitude quake that struck at 4:35 a.m. Saturday near the South Island city of 400,000 people. Most other buildings sustained only minor damage.Only two serious injuries were reported from the quake as chimneys and walls of older buildings were reduced to rubble and crumbled to the ground. Prime Minister John Key said it was a miracle no one was killed.Part of the reason the city escaped major injuries was because the quake happened before dawn, Key said."If this had happened five hours earlier or five hours later (when many more people were in the city), there would have been absolute carnage in terms of human life," he told TV One News Sunday.The quake cut power across the region, blocked roads with debris, and disrupted gas and water supplies, but Christchurch Mayor Bob Parker said services were being restored Sunday.Power was back to 90 percent of the city and water supply had resumed for all but 15 to 20 percent of residents, he said. Portable toilets have been provided and tanks of fresh water placed around the city for residents.Parker said it would take a long time to fully fix some core services such as water and sewage. "Our first priority is just people," he said. "That's our worry."Up to 90 extra police officers were flown into Christchurch to help, and troops were likely to join the recovery effort on Monday, he said.As the recovery work gathered pace, forecasters warned strong winds would buffet the area, creating problems with flying debris.WeatherWatch forecaster Philip Duncan said gale force winds of 40 mph (65 kph) and stronger "could cause serious issues for trees and buildings that were weakened in (Saturday's) huge earthquake."Specialist engineering teams began assessing damage to all central city buildings on Sunday, said Paul Burns of the city's search and rescue service. Officials said schools across the region would remain closed for the next two days to allow time to check whether they were safe.Canterbury University geology professor Mark Quigley said what "looks to us that it could be a new fault" had ripped across the ground and pushed some surface areas up. The quake was caused by the ongoing collision between the Pacific and Australian tectonic plates, said Quigley, who is leading a team trying to pin down the source of the quake."One side of the earth has lurched to the right ... up to 11 feet (3.5 meters) and in some places been thrust up," Quigley told National Radio."The long linear fracture on the earth's surface does things like break apart houses, break apart roads. We went and saw two houses that were completely snapped in half by the earthquake," he said.Roger Bates, whose dairy farm at Darfield was close to the quake's epicenter 19 miles (30 kilometers) west of Christchurch, said the new fault line had ripped up the surface of his land."The whole dairy farm is like the sea now, with real (soil) waves right across the dairy farm. We don't have physical holes (but) where the fault goes through it's been raised a meter or meter and a half (three to five feet)," he told National Radio."Trouble is, I've lost two meters (six feet) of land off my boundary," he added.Experts said the low number of injuries in the powerful quake also reflects the country's strict building codes."Thank God for earthquake strengthening 10 years ago," the Anglican dean of Christchurch, the Rev. Peter Beck, told TV One News on Sunday.Euan Smith, professor of Geophysics at Victoria University, speculated that the very soft soils of Christchurch had "acted like a shock absorber over a short period ... doing less damage to smaller buildings."Prime Minister Key, who flew to Christchurch to inspect the damage, said the city "looks like something off a movies set," with wrecked buildings, buckled roads, broken water mains and sewage systems and some flooding caused by broken water pipes.Scientists from GNS Science began installing 40 portable seismographs in the region Sunday to record seismic data from the continuing stream of aftershocks. More than 60 had been recorded by mid-afternoon Sunday.Seismologists study aftershock sequences to help learn more about the mechanics of the main quake, and to check whether stress in the Earth's crust has been transferred to other faults in the region.New Zealand sits above an area where two tectonic plates collide. The country records more than 14,000 earthquakes a year — but only about 150 are felt by residents. Fewer than 10 a year do any damage.New Zealand's last major earthquake registered magnitude 7.8 and hit South Island's Fiordland region on July 16, 2009, moving the southern tip of the country 12 inches (30 centimeters) closer to Australia, seismologist Ken Gledhill said at the time.