The person is not being ‘rewarded’ or ‘punished’ for their actions, their happiness or discomfort is simply a result of their actions.
‘How fortunate I am to have survived.’ She has suffered but she has not added to her suffering by being regretful, despairing or angry. Then she thinks, ‘There must be others much worse off than me. I must see what I can do to help,’
The woman’s positive thoughts and actions have now had a concrete positive effect on her life.
So according to Buddhism, the physical pain that the victims of the tsunami experienced is the outcome of various natural causes. How they are reacting to these natural causes is their kamma, the results of their negative or positive reactions in the future (tomorrow, next month, next year, perhaps next life), will be their vipaka.