Mechanical energy budget of a fold-and-thrust belt

Abstract

Recent studies^1,2 have shown that an active fold-and-thrust belt is mechanically analogous to the wedge of soil or snow that forms in front of a moving bulldozer; such a wedge attains a critical taper in which the regional state of stress is everywhere on the verge of brittle failure. Here this critical-taper model of the regional stress field is combined with a simple kinematic description of the steady-state deformation of an active, eroding fold-and-thrust belt, to examine the mechanical energy balance of brittle, frictional mountain building. Part of the work performed by the compressive stress at the rear of a fold-and-thrust belt is dissipated by frictional heating on the décollement fault, part is dissipated by internal frictional processes that accompany the brittle deformation within the critically tapered wedge, and part is expended against gravitational body forces. The total power expenditure in the steady-state fold-and-thrust belt of western Taiwan is about five gigawatts, of which 45% is being dissipated against basal friction, 39% is being expended against gravity and only 16% is being dissipated internally.