A global perspective on the topographic response to fault growth

Abstract

Precise factors controlling the coevolution of deformation and topography in tectonically active landscapes remain poorly understood due to complex feedbacks between numerous possible variables. Here we examine the links between fault kinematics, emergent topography, and environmental factors on a global data set of active fault-driven mountain ranges (n = 41). Using simple regressions between tectonic, climatic, and topographic variables, we explore the controls on faultdriven landscape development at the range scale. For each fault in our Google Earth accessible database, we compiled (1) topographic metrics from a 30-m digital elevation model including along-strike changes in elevation and relief, fault length, and tip zone length (the along-strike distance from fault tip to where the associated relief stops increasing) and gradient; (2) long-term (104-6 yr) tectonic variables including fault slip rate, displacement rate, displacement, and age, (3) climatic variables including annual precipitation; and (4) rock type from geologic maps. Our results show that all mountain ranges reach a uniform value of relief within some distance from their tips and the length scale of this relief growth correlates with long-term vertical displacement rate (R = 0.55) and slip rate (R = 0.51). We apply a well-established framework for fault growth as the tectonic boundary condition to estimate the time required to achieve this uniform relief (~104-6 yr) and suggest that this threshold time indicates regional tectonomorphic equilibrium. Strong correlations between annual precipitation and deformation rates (R > 0.60), and between lithologic strength and mountain relief (R > 0.70), allude to other principal forces affecting emergent landscape form that are often ignored. Our findings demonstrate that fault-driven topography always saturates in relief, suggest there are quantifiable fault-kinematic controls on landscape form, and hint that landscape relief patterns may, in turn, be used to estimate rates of faulting.