Superblock is nothing but 0th sector of your partition, which contains metadata. While running fsck you are actually retrieving this metadata. This will contain everything about your data(inode details and all) except data. Once this got corrupted you may be able to retrieve, depends on your luck. Superblock can be easily retrieved from the sectors where it is being backuped. You can use the following command.
e2fsck -b <blockno:> /dev/hdai
You can google for block numbers of backuped superblock.
I hope this will help you..