there are two factors for every decentralised cryptocurrency:
    – the ledger
    – keys for the cryptocurrency: practically the crypto money is stored on the ledger but you can access only with the keys.

    The ledger is stored at around 10000 nodes around the world, it is very unlikely such a catastrophe that all nodes go offline. And even if there is such an event, if some of the nodes come online the system works again.

    The other aspect is from the end-user and key perspective : the keys can be kept offline, like on a piece of paper, but one can spend the money only with online access to the ledger. If the keys are lost, the money is lost. So it is usually proposed to replicate the keys on multi continent geographical storage in order to prevent the lost in catastrophic events.

    Hey Gopinath 🙂 The architecture of cryptocurrency blockchains like Bitcoin are designed to survive catastrophic failures. This is achieved by data redundancy: hundreds of people on the blockchain network store copies of the full blockchain. Anyone can join the network and receive their own copy. This type of redundancy makes it very likely that the data will survive a catastrophic event in any part of the world since there would be many copies in other parts of the world. As long as there is one copy, many other copies can be created.