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.
Sometimes there are many small earthquakes before the big one. These small ones are called foreshocks. After the big earthquake, the mainshock, again there may be many small quakes. These are called aftershocks.
A magnitude 7 or higher can destroy a city.