Catastrophes and risks have had a great influence on the evolution of human development. We analyze behaviors in front of risks, then we consider some basic principles that have guided private and public behaviors. Managing risks has become a specialty for finance and insurance, but they are not the only institutions that allow to confront them. We conclude on an example of how public funds, private insurance and reinsurance companies can work together and use financial markets in order to cover financial risks due to seisms.