A magnitude 7 or higher can destroy a city.
The shaking of the ground is not what kills most victims of earthquakes. The main killers in earthquakes are falling buildings, fires, landslides, avalanches and tsunamis.
You would feel the ground shake in a magnitude 3 quake.
Steel, reinforced concrete and wood are good building materials for an earthquake resistant house because they flex somewhat without breaking. Family homes built completely out of brick are not as safe because they can break apart easily.