The evolution of folds-thrust wedges: Mathematical simulation based on finite difference method.

Various analogue models are applied to research the structural evolution of fold-and-thrust wedges. Numerical models are used to explore the fold-thrust wedges and some enlighting research has been made. But combination of the two models have rarely been given sufficient attention. Up to now, landward-vergent thrust wedges, which are uncommon in nature, have not yet been adequately explained and can only be reproduced in a few analogue models under particular conditions. In order to look closer at the formation conditions of fold-and-thrust wedges and to explore the origin of landward-vergent thrust wedges, we conducted a series of analogue and numerical models under different conditions of substrate. Results of our models revealed that in the frictional basal substrate, and under conditions of a large coefficient of frictional basal, it deformed the fold-and-thrust wedges. Purely landward-vergent thrusting wedge has formed, in the presence of an extremely weak or ductile basal decollement. The number of Landward-fault and fault displacement decreased, when the thickness of the ductile basal increased or the velocity decreased.