Name
From aseismic to seismic: Can we pin-point the elusive stress transition?
Date & Time
Tuesday, May 9, 2023, 2:15 PM - 2:30 PM
Rebecca Salvage
Description
Earthquake processes are thought to occur on a continuum from aseismic (stable sliding) to seismic slip (event nucleation), however the mechanisms causing any evolution between the two end-members is still not fully understood. Possible mechanisms may relate to dynamic fault weakening, static stress transfer, the concentration of shear stress at the boundary of an aseismic region, some combination of these, or a mechanism we have yet to detect. Moreover, the detection of aseismic processes is inherently difficult, adding to the challenges in detecting and understanding this evolution. Here, we investigate evidence for a critical state transition within the subsurface using data from several recent seismic sequences in western Canada that may relate to fluid injection. In both cases, the onset of seismicity is temporally offset from the initiation of fluid injection into the subsurface, suggesting that initial deformation was aseismic. At some point, deformation became seismic with an increase in the number of seismic events, although this temporal offset varies in the investigated sequences from months to years. Using an array of techniques, including ambient seismic noise, repeating seismicity and the identification of tremor-like signals, we determine whether there is evidence of a critical state transition from aseismic to seismic deformation at depth. The identification of such a transition is important, in particular during long-lived fluid injection experiments, for risk assessment.
Location Name
Aspen
Full Address
Banff Park Lodge Resort Hotel & Conference Centre
201 Lynx St
Banff AB T1L 1K5
Canada
Abstract
Earthquake processes are thought to occur on a continuum from aseismic (stable sliding) to seismic slip (event nucleation), however the mechanisms causing any evolution between the two end-members is still not fully understood. Possible mechanisms may relate to dynamic fault weakening, static stress transfer, the concentration of shear stress at the boundary of an aseismic region, some combination of these, or a mechanism we have yet to detect. Moreover, the detection of aseismic processes is inherently difficult, adding to the challenges in detecting and understanding this evolution. Here, we investigate evidence for a critical state transition within the subsurface using data from several recent seismic sequences in western Canada that may relate to fluid injection. In both cases, the onset of seismicity is temporally offset from the initiation of fluid injection into the subsurface, suggesting that initial deformation was aseismic. At some point, deformation became seismic with an increase in the number of seismic events, although this temporal offset varies in the investigated sequences from months to years. Using an array of techniques, including ambient seismic noise, repeating seismicity and the identification of tremor-like signals, we determine whether there is evidence of a critical state transition from aseismic to seismic deformation at depth. The identification of such a transition is important, in particular during long-lived fluid injection experiments, for risk assessment.
Session Type
Breakout Session