Geometry, displacement–length scaling, and extensional strain of normal faults on Mars with inferences on mechanical stratigraphy of the Martian crust

Abstract

We measure throw distributions for graben-bounding normal faults from two areas on Mars to investigate fault growth, displacement–length ( D max– L) scaling, and extensional strain using a complementary suite of techniques. Faults in the northern plains are inferred to be restricted at 2–3 km depth, as shown by a transition from linear scaling, with D max– L ratios of ∼1 × 10 −3, to nonlinear scaling for faults >50 km long. On the Alba Patera volcano, faults conform to linear D max– L scaling, with a D max– L ratio of ∼6 × 10 −3, consistent with more deeply penetrating faults that are not restricted at depth. These grabens accommodate larger extensional strains (∼0.84%) than the faults in the northern plains (∼0.23%), with a temporal change from regionally distributed to localized deformation and associated increases in D max– L ratio, extensional strain, and perhaps down-dip fault height. The results suggest that both spatial and temporal variations in extensional strain and displacement–length scaling relations, along with fault restriction, are recorded by Martian fault populations.