The Groundbreaking Experiment in Earthquake Control at Rangely, Colorado, Revisited.

Earthquakes caused by human activities are a growing societal concern. A pioneering study of induced seismicity in the 1970s involved cooperation between the U.S. Geological Survey and Chevron, Inc., to adjust operations in the Rangely oil field, Colorado, to initiate and control earthquakes. Here we revisit this experiment using coupled flow and geomechanical modeling to determine the physical mechanisms that caused these earthquakes and investigate the strength and state of stress acting on the fault that sourced them. The controlled nature of the Rangely experiment, combined with data from decades of field operations, presents a unique opportunity to understand the phenomenon of induced seismicity in ways that can be applied to manage these risks. Plain Language Summary: We revisit the classic field experiment conducted in the Rangely oil field, Colorado, to initiate and control the occurrence of earthquakes. Our study applies state‐of‐the‐art numerical modeling to investigate the physical mechanisms that caused these events. In addition, knowledge about the structure and state of stress at Rangely from decades of field operations enables us to determine the strength of the fault and the relative contributions of tectonic versus anthropogenic stress that led to these earthquakes. These insights suggest that modest perturbations to stress fields caused by field operations can trigger seismicity on long dormant faults that are far from active tectonic plate boundaries, which has important implications for assessing and managing risks associated with induced and triggered seismicity. Key Points: Our work revisits the classic experiment in earthquake control at Rangely, Colorado, to determine the physical mechanism that caused these earthquakesThe coefficient of friction for the earthquake‐sourcing fault at Rangely experiment is inferred to be ~0.70, consistent with Byerlee valuesWe define the tectonic and anthropogenic stress contributions that caused these events, thus distinguishing "Induced" versus "Triggered" seismicity [ABSTRACT FROM AUTHOR]