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Linking Spatiotemporal b-Value Evolution to Physical Mechanisms Influencing EGS Induced Seismicity

Description: 

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 Soultz-sous-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.

Session: Mechanistic Insights into Fluid-induced Earthquakes from the Laboratory to the Field [Poster]

Type: Poster

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Matthew

Student Presenter: Yes

Invited Presentation: 

Poster Number: 101

Authors