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Abstract In areas of induced seismicity, earthquakes can be triggered by stress changes due to fluid injection and static deformation from fault slip. Here we present a method to distinguish between injection‐driven and earthquake‐driven triggering of induced seismicity by combining a calibrated, fully coupled, poroelastic stress model of wastewater injection with interpretation of a machine learning algorithm trained on both earthquake catalog and modeled stress features. We investigate seismicity from Paradox Valley, Colorado as an ideal test case: a single, high‐pressure injector that has induced thousands of earthquakes since 1991. Using feature importance analysis, we find that injection‐driven earthquakes are approximately 225% of the total catalog but act as background events that can trigger subsequent aftershocks. Injection‐driven events also have distinct spatiotemporal clustering properties with a larger b‐value, closer proximity to the well, and earlier occurrence in the injection history. Generalization of our technique can help characterize triggering processes in other regions where induced seismicity occurs.
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This content will become publicly available on April 1, 2026
Linking Spatiotemporal b-Value Evolution to Physical Mechanisms Influencing EGS Induced Seismicity
The development and operation of Enhanced Geothermal Systems (EGS) can induce earthquakes during fluid injections, posing significant hazards for both local populations and the continued operation of EGS plants. An improved understanding of the interplay between the physical mechanisms affecting geothermal induced seismicity is important for current and future EGS projects. One way to analyze seismicity is with the b-value, which represents the slope of earthquake magnitude frequency distributions. Previous EGS studies suggest a pore-pressure driven induced seismicity model where spatially – the b-value is high near the injection point and temporally – the b-value decreases during later stages of injection. We evaluate the pore-pressure driven model by comparing the spatiotemporal b-value evolutions of nine different EGS induced seismicity scenarios including Basel and FORGE, along with injections from Soultzsous-Forêts and Cooper Basin. In our spatiotemporal analyses, we find that a majority of examined sequences have a period where the distal b-value is significantly higher than the b-value near the injection point. These sequences indicate that the pore-pressure driven model is inadequate for describing spatiotemporal b-value evolution, and that additional physical mechanisms, like aseismic slip, could have significant effects on EGS induced seismicity. Further characterization of the b-value in EGS induced seismicity sequences provides an opportunity to better constrain the degrees to which different physical mechanisms influence seismicity.
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- Award ID(s):
- 2315814
- PAR ID:
- 10631921
- Publisher / Repository:
- GeoScienceWorld
- Date Published:
- Journal Name:
- Seismological Research Letters
- Volume:
- 96
- Issue:
- 2B
- ISSN:
- 0895-0695
- Page Range / eLocation ID:
- 1241 to 1490
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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