Understanding Rupture Directivity of Injection-induced Earthquakes: A Numerical Study Coupling Poroelastic Model With Rate-and-state Earthquake Cycle Simulator
Description:
Understanding rupture directivity is crucial for assessing induced earthquake hazards, as it significantly influences the resulting ground motions. This study analyzes factors controlling the rupture process of induced events by integrating spatiotemporal fluid-induced pressure and stress perturbations from fully-coupled poroelastic models in COMSOL, into fully-dynamic earthquake cycle simulations based on the boundary integral method and rate-and-state friction law. The COMSOL model features a 2.75-km-long rectangular fault, with an off-fault injection of 10 kg/s lasting for ~8 days. The resulting maximum changes in Coulomb failure stress is ~100 kPa, comparable to perturbation values calculated in a prior study for the Delaware Basin due to shallow injections. On-fault pressure and stress perturbations are recorded for ~112 days post-injection until the perturbation drops by >99%. These data are introduced into a rate-and-state fault model for fully-dynamic simulations, under various injection start times, fault configurations, and background normal stress (2 - 60 MPa).
Results show that rupture directivity of induced events depends on the relative strength of pressure and stress perturbations in relation to background stress. When normal stress is relatively high (20 MPa), no correlation is observed between directivity and the induced pressure/stress gradient. In these cases, the nucleation location and direction of triggered events are primarily governed by the heterogeneous distribution of shear stress on the fault that is shaped by prior seismic and aseismic activities. In contrast, when normal stress is lower (2 MPa), most triggered aseismic transients and subsequent dynamic nucleation tend to occur in regions closer to the injection site with stronger perturbations and ruptures propagate away during the injection period. Overall, our findings emphasize the importance of the relative strength of perturbations to background stress in determining the nucleation patterns of induced seismicity. We will also discuss the role of triggered aseismic transients in constraining future earthquake locations.
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: Xinyu
Student Presenter: Yes
Invited Presentation:
Poster Number: 103
Authors
Xinyu Tan Presenting Author Corresponding Author xy.tan@mail.utoronto.ca University of Toronto |
Semechah Lui semechah.lui@utoronto.ca University of Toronto |
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Understanding Rupture Directivity of Injection-induced Earthquakes: A Numerical Study Coupling Poroelastic Model With Rate-and-state Earthquake Cycle Simulator
Category
Mechanistic Insights into Fluid-induced Earthquakes from the Laboratory to the Field