The swinging set off by the force of the earthquake could swing such items right off their hooks. An earthquake could shake them off the shelf, causing them to break on the floor. Consider a cabinet with latching doors, instead of shelves. Replace them with new latches that will hold during and earthquake. Put items stored in glass containers on lower shelves or to the back of the cabinet.
Some shelves have a shelf railing to prevent items from falling off.
Newspaper or cardboard should be recycled or thrown away. Block the wheels so the object cannot roll. Attach such furniture securely to the studs in the walls to prevent them from tipping over. In any sort of stress, the connection would break, flooding your home with toxic, explosive gas. Make sure they are well braced to prevent falling.