1. A method comprising: receiving values of a perturbed stress field associated with a fractured region of earth, the values calculated via at least three linearly independent numerical simulations; receiving values of at least three far field stress vectors, the values used as boundary conditions for the numerical simulations; based on the values of the at least three far field stress vectors, building and inverting a stress matrix that comprises columns representing the far field stress vectors to generate an inverted stress matrix; based at least in part on the values of the perturbed stress field and the inverted stress matrix, minimizing a cost function to compute values of a parameter vector; based at least in part on the values of the parameter vector, computing values of a paleostress vector associated with the fractured region of earth; determining a tectonic regime based at least in part on the values of the paleostress vector; and associating the tectonic regime with at least one fault of the fractured region of earth.