Injection‐Induced Seismic Moment Release and Laboratory Fault Slip: Implications for Fluid‐Induced Seismicity
Wang, Lei; Kwiatek, Grzegorz; Rybacki, Erik; Bohnhoff, Marco; Dresen, Georg, 2020: Injection‐Induced Seismic Moment Release and Laboratory Fault Slip: Implications for Fluid‐Induced Seismicity. In: Geophysical Research Letters, Band 47, 22, DOI: 10.23689/fidgeo-4018.
Understanding the relation between injection‐induced seismic moment release and operational parameters is crucial for early identification of possible seismic hazards associated with fluid‐injection projects. We conducted laboratory fluid‐injection experiments on permeable sandstone samples containing a critically stressed fault at different fluid pressurization rates. The observed fluid‐induced fault deformation is dominantly aseismic. Fluid‐induced stick‐slip and fault creep reveal that total seismic moment release of acoustic emission (AE) events is related to total injected volume, independent of respective fault slip behavior. Seismic moment release rate of AE scales with measured fault slip velocity. For injection‐induced fault slip in a homogeneous pressurized region, released moment shows a linear scaling with injected volume for stable slip (steady slip and fault creep), while we find a cubic relation for dynamic slip. Our results highlight that monitoring evolution of seismic moment release with injected volume in some cases may assist in discriminating between stable slip and unstable runaway ruptures.Plain Language Summary: Anthropogenic earthquakes caused by fluid injection have been reported worldwide to occur in the frame of waste‐water disposal, CO2 sequestration, and stimulation of hydrocarbon or deep geothermal reservoirs. To study the dynamics of injection‐induced seismic energy release in a controlled environment, we performed laboratory fluid injection experiments on critically stressed high‐permeability sandstone samples with a prefabricated fault. We monitored acoustic emission occurring during injection‐induced fault sliding. We find that the total seismic deformation (expressed as total seismic moment) is related to total injected volume, independent of fault slip modes (i.e., dynamic slip, steady slip, and fault creep). Seismic moment release rate roughly scales with fault slip velocity. In our experiments, the fluid pressure front migrates faster than the rupture front by about 5 orders of magnitude, resulting in fault slip within a zone of homogeneous fluid overpressure. We find that cumulative seismic moment scales linearly with the injected volume for stable slip (steady slip and fault creep), while it follows a cubic relation for dynamic slip. Our experimental results suggest that the deviation of cumulative moment release with injected volume from a linear trend in practice might be a sign for potential seismic risk. This may be considered in modifying current injection strategies.Key Points: Injection‐induced fault deformation is dominantly aseismic. Total moment release depends on total injected volume, independent of fault slip behavior. Moment‐injected volume scaling is linear for stable slip but shows a cubic relation for dynamic slip.
seismic moment release
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