How can you create multiple blogs with one email ID?
You can create and be a part of more than one blog using the same Email ID.
If you have created a blog then you will be called the "Admin' of that blog and have access to all features.
You can do so by clicking on "Create new account" in the top right corner of the screen.
If you have been invited to other blogs as a writer, editor, or any other role assigned to you and you chose to accept the invitation, then you are a part of those blogs as well.
You can read about this in detail here.