B-valuation: Linking High B-values at the Edges of EGS Injection Induced Seismicity With Aseismic Slip
Description:
Understanding the mechanisms of inducing seismicity within Enhanced Geothermal Systems (EGS) is important for ensuring the safety of local populations and continued operation of EGS projects. The classically favored dominant mechanism is a direct pore pressure effect, which can induce earthquakes by lowering effective normal stress. However, more indirect mechanisms, like aseismic slip resulting from pore pressure perturbations, may have more a dominant role in inducing seismicity. To better characterize the mechanisms influencing EGS induced seismicity, we conduct spatiotemporal analyses of 9 different EGS injection sequences. We utilize the b-value – as a measure of magnitude distribution and a proxy for stress – to examine spatiotemporal variations by splitting earthquakes into equal-event groups or “shells” based on distance from the injection point. Additionally, for the different injection sequences, we compute and analyze b-value variations of their seismicity fronts, defined by the outermost earthquakes from the injection point over time and which can be controlled by fluid pressure diffusion and fluid-induced aseismic slip mechanisms. We find that many sequences exhibit a period of high b-values close to the seismicity front, contrary to pore pressure model expectations. Across the different sequences we see the overall seismicity front b-values range from coequal to significantly higher than that of the remainder of the respective sequences. We suggest that these extremely high b-values are influenced by aseismic slip, and that sequences with extremely high seismic front b-values result from a self-sustaining aseismic slip mechanism controlling the seismicity front. This implies that aseismic slip has a crucial influence on EGS injection induced seismicity and should be accounted for in subsequent EGS projects and research.
Session: From Drilling to Ground Shaking: Mechanisms, Monitoring and Mitigation of Induced Earthquakes [Poster]
Type: Poster
Date: 4/17/2026
Presentation Time: 08:00 AM (local time)
Presenting Author: Matthew P. Salinas
Student Presenter: Yes
Invited Presentation:
Poster Number: 100
Authors
Matthew Salinas Presenting Author Corresponding Author mpsalina@usc.edu University of Southern California |
Yihe Huang yiheh@umich.edu University of Michigan |
Louis De Barros debarros@geoazur.unice.fr Côte d'Azur University |
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B-valuation: Linking High B-values at the Edges of EGS Injection Induced Seismicity With Aseismic Slip
Category
From Drilling to Ground Shaking: Mechanisms, Monitoring and Mitigation of Induced Earthquakes