Pore Pressure Diffusion and Onset of Induced Seismicity

The Raton Basin of Southern Colorado and Northern New Mexico experienced a significant increase in seismicity over the last several decades, including two M5+ earthquakes. The increase in seismicity started soon after an increase in wastewater disposal associated with coal-bed methane production. Twenty-nine wastewater injection wells have operated in the Basin, with several high-rate injectors located within a kilometer of the most seismically active regions. We developed a pore pressure model to investigate the relationship between pore pressure diffusion and onset of induced seismicity, with an emphasis on the Trinidad fault zones. Our model indicates that sufficient pore pressure increase had accumulated on the northern extent of the Trinidad fault zone to induce seismicity at the time of early-stage seismic activity. The hydrogeologic architecture of the Basin played a key role in controlling pore pressure perturbation. The basal sedimentary interval with moderately low diffusivity restricted vertical pore pressure diffusion, creating a substantial lag time between wells becoming active and the expression of perturbation in the fault zones. The spatiotemporal relationship between early-stage seismicity and wastewater injection in conjunction with modeled pore pressures suggests that the early-stage seismicity in the Raton Basin was likely triggered by pore pressure diffusion.

Automated summary

The Raton Basin in Southern Colorado and Northern New Mexico has experienced a significant increase in seismic activity over the last few decades, possibly due to an increase in wastewater disposal from coal-bed methane production. The presence of high-rate injection wells near the most seismically active regions suggests a possible correlation. A pore pressure model was developed to study the relationship between pore pressure diffusion and induced seismicity, particularly focusing on the Trinidad fault zones. The model suggests that the early-stage seismicity in the Raton Basin was likely triggered by pore pressure diffusion.