ESTIMATING BASAL FRICTION IN ACCRETIONARY WEDGES FROM THE GEOMETRY AND SPACING OF FRONTAL FAULTS

Abstract

Elastic theory applied to the deformation in accretionary wedges is used to calculate the condition for slip along an active frontal fault and the basal decollement. The equations for calculating the stresses can be solved for the coefficient of basal friction in the situation of the formation of a new frontal thrust fault. This allows us to calculate the efficient coefficient of basal friction, which includes the weakening effect of pore-fluid pressure, from geometric parameters and material properties only. The geometric parameters, like fault dip and layer thickness, can be derived from high-resolution seismic cross-sections. Application of our analysis to the Makran and the Nankai accretionary wedge allows us to estimate the upper limit of the effective coefficient of basal friction, μb~0.16 and μb~0.2, in these two areas respectively.