I'd find that more credible of a single instance, but New Madrid + Tunguska + Krakatoa + Casaverde + the suggestion that there have been many others ? That's a heck of a debt for him to be reacking up, no ?
It certainly is, while I'm not saying I firmly believe in this idea, I think it could certainly create some interesting plot twists of the sort that would cause Kincaid and Eb to have a deep distaste for each other rather than the more frequent professional detachment.
Of course he could use any number of methods. It might even be that he uses whichever fits, for example some sort of entropy curse for the satellite, or on the castle itself the satellite being a random bad thing. A bit of vulcanomancy where it's needed. OH no, those people aren't sitting on a fault line, hey you, mind destroying that bit of land?
Is there any way of knowing how old Eb was when he caused the first catastrophe directly attributed to him?
Those Porn-star sorceresses, were they racking up a debt

Sigh I need to read these books again.