Present‐Day Stress Field Influences Bedrock Fracture Openness Deep Into the Subsurface

Abstract Fracturing of bedrock promotes water-rock interactions and influences the formation of the life-sustaining layer of soil at Earth’s surface. Models predict that present-day stress fields should influence bedrock fracture openness, but testing this prediction has proven difficult because comprehensive fracture datasets are rarely available. We model the three-dimensional present-day stress field beneath the deglaciated, low-relief landscape of Forsmark, Sweden. We account for ambient regional stresses, pore pressure, topography, sediment weight, and seawater loading. We then compare the modeled stresses to a dataset of ~50,000 fractures reaching depths of 600 m at Forsmark. We show that modeled failure proxies correlate strongly with the fraction of observed open fractures to depths of ~500 m. This result implies that the present-day regional stress field, affected by surface conditions and pore pressure, influences fracture openness in bedrock hundreds of meters beneath the surface, thereby preparing the rock for further weathering.