Scaled Experimental Models of Extension: Dry Sand vs. Wet Clay

Abstract

The choice of modeling material—dry sand or wet clay—affects the style and distribution of deformation in scaled experimental (analog) models of extension. For example, fault-zone widths are greater in sand than in clay, possibly reflecting the marked difference in maximum grain size of the modeling materials (<0.5 mm for dry sand vs. < 0.005 mm for wet clay). Most differences in the deformation patterns, however, reflect differences in the ductility of the modeling materials. Normal faults are long, planar and hard-linked (i.e., directly connected) in the dry sand with its low ductility, whereas normal faults are short, curved and soft-linked (i.e., not directly connected) in the wet clay with its higher ductility. A few large normal faults accommodate most deformation in the sand models, whereas a few large faults and numerous small faults accommodate most deformation the clay models. Little folding occurs in the sand models, but folds are common in the clay models.