This is why God allows natural disasters and terrible suffering

Public and national sins must be expiated in this world for the very simple reason that they cannot be expiated in the next.

In the world to come families, cities, provinces and nations will have no continued corporate existence. 

There, men and women will exist merely as individuals, without being united by those social, civil, political and national bonds which are necessary in this life for the welfare and preservation of the human race. 

In eternity, they will individually enjoy the fruits of their life on earth – the good will possess the kingdom of God in heaven, while the wicked shall suffer for their evil deeds in the unquenchable fires of hell. 

But as public sins require public expiation, and this expiation cannot be made in this next life, it is clear that it must be made on this side of the grave.

(From Father Remler, Why must I suffer?)