Injection-Induced Seismicity in the Northern Delaware Basin: 7.5 year Retrospective of the US Midcontinent’s Most Active Fault System

ABSTRACT: Recent seismicity in the northern Delaware Basin of Texas and New Mexico provides a rich laboratory to understand the cause of injection-induced seismicity. More than 8,000 earthquakes of ML 2.0+ occurred in the period Aug 2017 – Apr 2025, including more than 10 above ML 4.5. Several studies have mechanistically linked both deep and shallow injection to earthquakes that are occurring primarily in the geologic basement. However, deep injection is currently believed to be the primary cause of seismicity on deep basement-rooted faults. In the most seismically active area of the basin, the North Culberson-Reeves Seismic Response Area (NCR SRA), elevated earthquake rates are associated with modest (˜15 MMbbl/month) local deep injection rates, indicating that the system is highly sensitive to earthquake triggering from distal injection. Recent and significant reduction in deep injection rate and a corresponding reduction in earthquake rate provides insight into prevailing causal mechanics. Here we integrate findings from multiple modeling approaches to study injection-induced fault rupture and seismicity in the NCR SRA region. Pore pressure diffusion modeling using detailed geological models indicates that small (˜100 kPa) pore pressure changes can lead to rupture of sensitive faults, some at distances of 10s of km from injection centers. Recent modeling using the Geomechanical Injection Scenario Toolkit with analytical solutions for pore pressure diffusion and poroelastic stressing indicates that the relative roles of these causal agents at earthquake locations is highly dependent on injection zone net reservoir thickness and reservoir diffusivity. High-resolution earthquake data provides insights into earthquake sequence onset and evolution, including evidence for long-distance diffusion along seismogenic faults and migration of seismicity along fault strike and with depth. Ensemble model temporal forecasts that use pore pressure diffusion models as input show a good fit to the observed earthquake catalog, which highlights the value of utilizing comprehensive geological and pore pressure models as input to seismicity rate forecasts.