Displacement accumulation from earthquakes on isolated normal faults

Displacement profiles for isolated normal faults are most often triangular rather than semi-elliptical as predicted for linear elastic materials. Simple modelling indicates that triangular displacement profiles can arise from Gutenberg–Richter earthquakes randomly distributed on fault surfaces of constant dimensions. Near-triangular profiles are generated after a small number of earthquake cycles and for earthquake magnitude ranges as small as 0.5. The results are only weakly dependent on the shape of earthquake slip profiles, and reproduce the geometry of displacement profiles on the non-propagating active Cape Egmont Fault in New Zealand. By contrast, growth models in which fault displacement and length increase in proportion result in unrealistic displacement profiles for realistic slip profiles irrespective of whether earthquake populations are Characteristic or Gutenberg–Richter.