How the energy budget scales from the laboratory to the crust in accretionary wedges

Abstract

We investigate the scaling properties of the mechanical energy budget in accretionary prisms across five orders of magnitude, from the laboratory centimeter-scale to crustal kilometer-scale. We first develop numerical models that match the length scale, fault and material properties, surface topography, and fault geometries observed in scaled dry sand accretionary experiments. As we systematically increase the spatial dimensions of the numerical models by orders of magnitude, we calculate each component of the energy budget both before and after the first thrust fault pair develops. The increase of both the bulk stiffness and slip weakening distance from the laboratory- to crustal-scale produces a scale-invariant partitioning of the energy budget, relative to the total work done on the system. The components scale as power laws with exponents of three. Consequently, accurate laboratory simulations of the energetics of deformation within crustal accretionary wedges require careful scaling of the stiffness and slip weakening distance. Preceding thrust fault development at both the laboratory and crustal scale, the internal work consumes the largest portion of the budget (67-77%) and frictional work consumes the next largest portion (17-27%). Following thrusting, frictional work and internal work consume similar portions of the energy budget (38-50%). The sum of the remaining energy budget components, including gravitational work, seismic work, and the work of fracture propagation, consume <10-15% of the total energy budget preceding and following thrust fault development.