Try this little experiment:

1. Break a block of foam rubber in half.
   
   
2. Put the pieces on a smooth table.
   
   
3. Put the rough edges of the foam rubber pieces together.
   
   
4. While pushing the two pieces together lightly, push one piece away from you along the table top while pulling the other piece toward you.
   See how they stick?
   
   
5. Keep pushing and pulling smoothly.

   Soon a little bit of foam rubber along the crack (the fault) will break and the two pieces will suddenly slip past each other. That sudden breaking of the foam rubber is the earthquake. That's just what happens along a strike-slip fault.