How should the Ummah respond to a calamity that strikes?

Q: What is the Islamic viewpoint on earthquakes? What should our attitude be towards the people who have suffered earthquakes? Should we blame the people or should we help them?

There are people who say that we should not help those who have suffered natural disasters because they have committed a sin, that is why they are facing this calamity. Is this a correct opinion?

Clarification: Will the Vat amount be included in the zakaat?

Q: A person gave me R100 of his zakaat and asked me to buy a zakaat hamper and give it on his behalf to the poor. I bought the hamper for R100 which was inclusive of 15% vat and thereafter gave it to a recipient of zakaat. Did R85 of the person's zakaat get discharged or did R100 of His zakaat get discharged?

Similarly, if zakaat vouchers are given to the poor and they make purchases with it from a specific shop to which zakaat money has been given, and the shop owner has been informed that he should give the poor who come to him items to the value of the zakaat vouchers, and the shop owner sells them the items for the full amount of the zakaat vouchers but deducts 15% of the money for vat, will the full amount of the zakaat vouchers be regarded as the zakaat discharged or will the amount less 15% be regarded as the zakaat discharged?