With the emergence of software defined networking and network function virtualization technologies, network services are expected to be offered as service function chains made out from virtual network functions that are connected to steer and process the incoming traffic. In this context, achieving the survivability of these chains against failures is a key challenge to ensure high availability and continuity of the services. A promising solution proposed in the literature is to provision backups for the virtual network functions that could be shared among multiple service chains. These backups are used in case of a failure to take over the failed functions and ensure service continuity. In this paper, we propose two solutions to efficiently place and provision the shared backups in order to ensure the survivability of the service chains against single node failures. The originality of these solutions is that they leverage the migration of virtual network functions to minimize the resources consumed by the backups. Simulation results show that, compared to existing solutions, the proposed schemes leveraging migration are able to reduce by up to 20% the amount of resources allocated for the shared backups while ensuring the survivability of the service chains.