First, spare your younger children the details. They need not--and should not--see graphic photos in order to make it "real" for them. That is unnecessary; younger children simply cannot digest that kind of information. It would hurl them into an existential crisis that they cannot handle. Older children can read newspaper accounts, but I would still have them avoid graphic photographs. Forget cable news reports of the disaster.
Second, give them some semblance of control and power. Perhaps you could offer to arrange a contribution from your child or your family to a reputable charity to help those suffering in Haiti. If that is impossible, your child could write an encouraging letter to a Haitian child. Praying for those suffering is also a way to help children feel involved, albeit in a safe way.
Third, reassure your young child that events like this are rare. Monumental disasters are not unrealistic, but young children need reassurance that things like this aren't happening on a regular basis. Older children can understand that earthquakes are infrequent in most places--save the west coast--and that most of them are relatively benign.
Fourth, let them know that you have plans for keeping them safe from disasters. If a disaster befalls you, Mom and Dad have a safety plan. If something happens to the house, you have a plan; if something happens to Mom or Dad, you have a plan to take care of them; and so on. If you don't have a safety plan, make sure you make one!
Finally, recognize that your children may suffer some from learning about these events. This is normal. In a strange way, it is beautiful that they might suffer along with the victims of this tragedy. Be thankful that your child has empathy. If it becomes so acute that he or she cannot sleep, eat, or function, then it's time to seek help and communicate with the child's teachers. But don't imagine that you can or should protect your child from all of the pain surrounding these and similar events.