Modal logic is the logic of possibility, contingency, and necessity. As a philosopher, I'm interested in which scientific disciplines investigate modal logic.
If you look at the proceedings of Advances in Modal Logic conference, you can see that contributions are split from mathematicians, computer scientists and philosophers. Mostly it depends on the interpretation of modalities scholars in disciplines other than philosophy are interested. For example, when modality is understood as provability in Peano Arithmetic mathematicians are definitely interested (and they have developed the so called Gödel Löb modal logic of provability, see the seminar work by George Boolos). Mathematicians also study the mathematical properties of the semantics associated to modal logic (possible world semantics as mathematical structures, actually some to first semantics for modal logic were developed in algebra, boolean algebra with operators McKinsey Tarski). Also, under the temporal interpretation computer scientists study modal logic (more specifically, temporal logic, CTL, CTL* and LTL and variants). Legal scholars study modal logic under the deontic interpretation, and social scientists interpretations where the modalities refers to agents.