Using intraday data, are there certain measures that exist for measuring the "activity" of a particular instrument. By intraday data I mean, all changes to the limit order book (trades, adds, cancels, etc.), tick by tick.
For example, let's say on any average day, this "measure of activity" for Apple stock would be relatively similar, but on a day where Apple is making an earnings release or some big event, I'd expect there to be more trading activity (maybe more adds/cancels, etc.) .
Are there any particular measures that can help me determine this?