Why We Care About Some Brown People but not Others

I just don't get why we get emotionally (often = $ (units aid)) involved in some natural disasters and not others. In the last year alone 20,000 people were killed in Iran and 10,000 killed in Venezuela (not to mention this one). Why is there such attention to the tsunami? Is it because the death toll is four times higher than a large disaster? Is it because it was an inter-continental disaster? Is it because people are in the mood to care? It is really funny that one day the Media tells us "20,000 people died today, don't get too worked up" and then some time later they say "40,000 people died, you don't care? What are you, some kind of monster?"
Obviously no one says this explicitly, but it is implicit. It is primarily told by how many days running stories are carried. Stories that are only told for one day are the "shock and forget" kind, whereas the week long ones are the "shock and care" kind. So when the tsunami hit I expected a "shock and forget" story (initial reports were only of 2,100 dead- NYT) but it was in fact a "shock and care" story. I now have to reorient my whole emotional approach (not to mention how I discuss the topic). Whose editorial job is it to tell me when I should care?!!!
(I should have personalized the title- but I can't take that much responsibility for myself)