I remember a philosophy seminar a-wayy back, where folks were arguing that the degree of cooperation during a disaster was a good measure of the social health of a community. There are many, many factors, though.
Japan has many advantages in this respect. They have a culture that has grown up with regular disasters, and have a tradition to live up to. They have a strong sense of belonging to their community. They are also influenced by their geography to make small communities in whatever little patches can be built upon. Even in the cities, it was traditionally organised by more-or-less self-contained neighbourhoods.
In Australia, there is usually a *little* looting after a disater, but much more community helping. In the US, I'll hazard the guess that there would be a bit more looting, but still quite a lot of helping. I guess the larger population and greater emphasis on individualism are factors.
I'll shut up now before I provoke too many of you trigger happy gun-totin' Yanks.