1. A method of simulating a subterranean region comprising: generating an initial finite element mesh over a domain representing a subterranean region, the finite element mesh defining elements representing respective sub-regions of the subterranean region, the elements comprising (a) a first element having a boundary defined by the finite element mesh and (b) a first node and a second node, at least a portion of the boundary representing a discontinuity in the subterranean region; performing a fracturing operation on the subterranean region to at least one of generate a new fracture and modify an existing fracture to provide a modified existing fracture; generating a modified finite element mesh based on the initial finite element mesh in order to model the at least one of the new fracture and the modified existing fracture; merging the first node into the second node in the modified finite element mesh in response to a distance between the first node and the second node being less than a threshold distance; generating a boundary element mesh over the boundary of the first element of the modified finite element mesh; by operation of one or more processors, simulating the subterranean region using the modified finite element mesh and the boundary element mesh by discretizing a first model of the subterranean region comprising a first system of equations in the time domain in accordance with a series of selected time steps to provide a second model comprising a second system of equations for each time step that is independent of time, the first model representing at least one physical process of the subterranean region; and solving the second system of equations to provide a simulation output; and at least one of performing an injection treatment on the subterranean region and drilling a borehole in the subterranean region in accordance with a selected trajectory based on the simulation output.