While significant, I would not consider a 6.2 magnitude earthquake to be "powerful." Still, tell that to the victims in Italy. Three towns in central Italy were devastated.
The Northridge earthquake in Los Angeles in 1994 was a 6.7 (which would make it approximately five times more powerful than the earthquake in Italy). The Northridge earthquake killed about seventy people and damage was well into the tens of billions of dollars.
The Richter Scale, while relatively precise means of measuring the power of a particular earthquake in some ways, does not necessarily translate to the damage caused by a particular tremor on the surface. That depends on how deep the fault was, the soil and geological conditions, how building are constructed and other factors. Seismologist use other scales, such as the Moment Magnitude Scale, to try to capture some of that.
Given how geologically active Italy is, you would think existing buildings would be more robust if only because many of the buildings are old and they have been exposed to big earthquakes in the past. Then again, building codes in Italy are probably not followed the same as they are in California.
My prayers and best wishes to the survivors.
Death toll exceed 120. Search for survivors continues...
Scientific American: Why the earthquake in Italy was so destructive
Jawa Report: Video from Italy
Daily Mail: Dramatic Rescue of a child, death toll rises above 240
Hot Air: Death Toll Over 250