Slow Strike-Slip Faulting in a Hyper-Arid Landscape: Assessing the Geomorphic Response to the Salar Grande Fault, Atacama Desert, Chile

Abstract

Geomorphic features near strike-slip faults, including offset channels, have long been used in paleoseismology. Recent numerical models suggest that slip rate information can also be expressed far upstream of faults as catchments respond to stream lengthening and shortening due to stream captures along the fault. Slow-moving faults show dynamic catchment-wide responses with migrating ridges and changing basins, whereas fast faults have more stable basins and distinct topography near and far from faults. Such patterns hold promise for revealing slip rate and geomorphic process information but have yet to be tested in end-member slip rate and climate environments. In this study, we examine the Salar Grande Fault (SGF) in the hyper-arid core of the Atacama Desert. We use InSAR to provide a first quantitative estimate of slip rate for the SGF of 0.2–0.6 mm/yr. We then analyze topographic profiles parallel to the fault, located near and far from it (Profile Relief Ratio (PRR)) and cross-divide metrics on fault-perpendicular ridgelines as proxies for ridge mobility and relative slip rate. Our results show that the hillslopes and channels respond to slow strike-slip faulting, even in a hyper-arid environment. However, the low erosion conditions do diminish the magnitude of the landscape response, yielding a PRR value indicative of a relatively faster-moving fault. These findings improve our understanding of the geomorphic response to strike-slip faulting and emphasize the importance of considering climatic and erosive conditions when assessing relative slip rates.