Inversion of stresses from polyphase fault/slip data with high or low diversity: An updated version of INVSFS

Fault/slip data with low diversity show limited range in orientation, and their equations, according to the Wallace–Bott hypothesis often give rise to an unstable stress solution. It is necessary in this case to introduce some auxiliary constraint(s), so as to make a stable stress solution from these equations. A new method for inverting stress from polyphase fault/slip data with low diversity but having all or a majority of newly formed faults in each subset is developed in this paper. It combines a weak criterion that favors the newly formed faults, together with the Wallace–Bott hypothesis or the strong criterion. Both criteria are solved for stresses using the Fuzzy C-lines clustering analysis technique. This permits the updating of the INVSFS code (Li et al., 2005). Two artificial sets of polyphase fault/slip data with high and low diversity are chosen to demonstrate the performance of the updated version.