Numerical Investigation of the Energy Budget of Fault Evolution within Experimental and Natural Thrust Systems

We use a Boundary Element Method numerical code to mechanically illustrate the transition between accretion and underthrusting as well as the energy balance during the evolution of fold and thrust belts. The mechanics of thrust nucleation and slip is controlled by complex interaction between work against gravitational forces and shear resistance along fault surfaces. This interaction reflects a trade-off between the amount of energy dissipated as internal strain and that absorbed via frictional heating on the faults. Our models investigate snapshots of infinitesimal deformation to simulate both analog experiments and natural case scenarios, such as at the Cascadia subduction margin. In each of these snapshots, we observe locations of shear localization indicative of incipient thrusting and the relative efficiency of forethrusts and backthrusts. Both the location and vergence of thrust faults matches analog and natural examples, suggesting that thrust development can be predicted with an internally consistent energy budget approach.