Which of these question tags is most appropriate for
There has been an earthquake. You must have felt it too, __ ?
– , haven’t you?
– , didn’t you?
– , mustn’t you?
First, the terminology. Wikipedia deems tacked-on questions other than those mirroring the grammar of the statement (eg “, yes?”) to also qualify as tag questions.
Second, what questions can be tagged onto “You must have felt it too”?
Certainly the suggestions given not containing a verb (“, correct?” / “, right?” / “, yes?” / “, no?”) and recasts (” … you did, didn’t you?”) are all quite acceptable.
“haven’t you” doesn’t work with a single event (an earthquake). It would work here: “There have been several smallish earthquakes this month. You must have felt them too, haven’t you?” [“, didn’t you?” also works here]
“didn’t you?” does work here: “I was woken by quite a pronounced tremor last night. You must have felt it too … didn’t you?” [the pause disguises a certain awkwardness resulting from the verb switch]
But “mustn’t you” would only be used in a situation like this to persuade someone of what seems inescapable but which they’re unsure about, rather than purely to check on facts:
“You must have left it at Auntie Jane’s, mustn’t you?” [two levels: solicitous or browbeating]
(ie “you’ve got to agree that it’s what actually happened”. The ‘must’ in “You must have felt it too” holds far less conviction; the tag question is proof of that. So “, mustn’t you?” is unavailable after “You must have felt it too” here as it defaults to a different sense.)