Accumulation of permanent deformation during earthquake cycles on reverse faults

A two-dimensional viscoelastic finite element model with a discrete stick-slip thrust fault is used to investigate tectonic strain accumulation and release associated with repetitive earthquakes. Results show that although interseismic and coseismic motions are opposite in sign, they generally do not completely cancel each other over a seismic cycle, as normally presumed in elastic rebound theory. Complete elastic strain release adjacent to dip-slip faults is inhibited by gravity, so that permanent deformation accumulates in the lithosphere with time. In the models, this permanent deformation is observed at the surface as large-scale upwarping of a hanging wall anticline and depression of an adjacent footwall foreland basin. The results are supported by observation of similar features adjacent to reverse faults in active collisional mountain belts and along the coastal margin of some modern subduction zones