Life is returning to normal in Chile's second city a month after the huge quake, but locals still tremble at every aftershock and worry even more when all goes quiet: the next one could be bigger.

"I bet that was a 4.9," said Nelson, sitting at home in Concepcion. "It had to be a 5.0," argued his friend Juan.

The hundreds of tremors from one of the strongest quakes on record have turned the coastal city's residents into earthquake experts. Moments later seismologists proved Juan was right in his estimate.

The predawn, 8.8-magnitude quake and tsunami on February 27 killed 452 people, left nearly a hundred missing and many more homeless.

It left a trail of damage estimated at about 30 billion dollars, as thousands of residents slowly try to repair their lives.

In Concepcion, called "The Gray One" for its dreary climate and dull architecture, reconstruction is now a way of life: excavators and trucks grind down the mountains of rubble, workers hammer away at roofs, electricians fix public lighting.

Coffee houses still hum with talk of "the big one."

More than 400 aftershocks have followed the February quake, keeping nerves always on edge.

In a sign that things are still not normal, a 6.2-magnitude earthquake hit northern Chile on Friday, causing hundreds of people to flee their offices and schools, and setting off car alarms.

Chilean seismologists said the tremor was not an aftershock as it happened along a different fault line than last month's quake.

After the looting that followed last month's quake, Concepcion's half a million inhabitants are trying to put the catastrophe behind them, a difficult task for many robbed of their livelihoods.

"In the mall, people go shopping, while we sit here and suffer. It's like we've been forgotten, like nothing ever happened," said Daniel, whose workplace collapsed.

The unscathed and the destitute live here side by side. Amid the rubble, the streets torn up by when the earth ripped apart and the condemned buildings, shoppers go in and out of stores and cars choke the streets at rush hour.

A 15-story apartment building that toppled, killing 10 people and leaving 80 survivors, has become both symbol of the tragedy and tourist attraction.

At the city's entrance, 35 families are still camped out in tents. Their building was left standing but cracks run up and down the walls and the families are afraid to go back inside.

About 70,000 other families in Chile are still waiting for the temporary housing promised them by authorities.

"We know other people suffered more, but we can't take it any more living in this camp, with all the rats, disease and our lives on the mend," said Roberto, whose pregnant wife broke a foot jumping from their second-story apartment after the quake.

After every major aftershock, Roberto walks to his former home to see if the building is still standing.

Even among those untouched by the tragedy, February 27 is seared in their memories.

"I've heard the Earth is trying to settle back with each aftershock. If this goes on, the city could literally open up beneath us, it could turn into an island or even disappear altogether," said Luis.

"If there are no tremors for several hours, it's dangerous. It means a big shock is coming," chimed in Juan Bernales.

A police officer joined the conversation: "People are getting on, but they're worried by what they hear on the news, by the possibility something worse could happen."

Well-armed soldiers, meanwhile, patrol the streets in groups of two or three, making sure tensions do not spill over and that people respect the curfew, which has now been reduced to just seven hours, from 11:00 pm to 6:00 am.

People have welcomed them. After all the post-quake chaos and anarchy, the 15,000 troops are a welcome sight.

"The people thank us for being here and, in general, they don't tell us they want us to leave the city," said a young soldier as he made his rounds.