I have no idea how that scale works. It didn't feel that strong up north. The first time I felt one, I freaked out, and then I went downstairs to people having breakfast who told me if I wasn't laying in my bed, I wouldn't have even noticed. :\
i assume the melbourne CBD was not the epicentre
probably out to sea, so out to sea it was 5.2 and diminishing returns as you go further away