A relationship between the cumulative elastic driving stress (or far-field elastic differential stress) and the inelastic strain of a fault population can be defined from the displacement-length scaling relations of the population. Two solutions are presented: one in which the elastic parameters remain constant, and the other that assumes a progressive reduction in modulus with increasing fracture spatial density. The method is illustrated by using fault populations from Mars. Cumulative differential stresses of 37 MPa and 87 MPa (computed here for 1 km depth) are implied to have produced the strains observed at Amenthes Rupes (widely spaced thrust faults) and Tempe Terra (closely spaced normal faults), respectively.