Earthen Might

Earthen Might is a  passive skill in Diablo III, unlocked at level 64.

In-game
This applies to all forms of casting, even those triggered by the combination of Might of the Earth set and, or with Blade of the Tribes.

Note that Earthquake does not generate Fury instead of spending it, but rather refunds 30 Fury after cast, effectively generating Fury per cast (normally 5 each time). With The Mountain's Call rune, turns Earthquake into Fury generator.