TY  - JOUR
A1  - Wang, Lei
A1  - Kwiatek, Grzegorz
A1  - Rybacki, Erik
A1  - Bonnelye, Audrey
A1  - Bohnhoff, Marco
A1  - Dresen, Georg
T1  - Laboratory study on fluid-induced fault slip behavior: the role of fluid pressurization rate
JF  - Geophysical research letters : GRL
N2  - Understanding the physical mechanisms governing fluid-induced fault slip is important for improved mitigation of seismic risks associated with large-scale fluid injection. We conducted fluid-induced fault slip experiments in the laboratory on critically stressed saw-cut sandstone samples with high permeability using different fluid pressurization rates. Our experimental results demonstrate that fault slip behavior is governed by fluid pressurization rate rather than injection pressure. Slow stick-slip episodes (peak slip velocity < 4 mu m/s) are induced by fast fluid injection rate, whereas fault creep with slip velocity < 0.4 mu m/s mainly occurs in response to slow fluid injection rate. Fluid-induced fault slip may remain mechanically stable for loading stiffness larger than fault stiffness. Independent of fault slip mode, we observed dynamic frictional weakening of the artificial fault at elevated pore pressure. Our observations highlight that varying fluid injection rates may assist in reducing potential seismic hazards of field-scale fluid injection projects. <br /> Plain Language Summary Human-induced earthquakes from field-scale fluid injection projects including enhanced geothermal system and deep wastewater injection have been documented worldwide. Although it is clear that fluid pressure plays a crucial role in triggering fault slip, the physical mechanism behind induced seismicity still remains poorly understood. We performed laboratory tests, and here we present two fluid-induced slip experiments conducted on permeable Bentheim sandstone samples crosscut by a fault that is critically stressed. Fault slip is then triggered by pumping the water from the bottom end of the sample at different fluid injection rates. Our results show that fault slip is controlled by fluid pressure increase rate rather than by the absolute magnitude of fluid pressure. In contrast to episodes of relatively rapid but stable sliding events caused by a fast fluid injection rate, fault creep is observed during slow fluid injection. Strong weakening of the dynamic friction coefficient of the experimental fault is observed at elevated pore pressure, independent of fault slip mode. These results may provide a better understanding of the complex behavior of fluid-induced fault slip on the field scale.
KW  - fault slip
KW  - fluid injection
KW  - induced seismicity
KW  - fluid pressurization
KW  - rate
KW  - stick-slip
KW  - fault creep
Y1  - 2020
U6  - https://doi.org/10.1029/2019GL086627
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 6
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Wang, Lei
A1  - Kwiatek, Grzegorz
A1  - Rybacki, Erik
A1  - Bohnhoff, Marco
A1  - Dresen, Georg
T1  - Injection-induced seismic moment release and laboratory fault slip
BT  - implications for fluid-induced seismicity
JF  - Geophysical research letters
N2  - 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.
KW  - induced seismicity
KW  - seismic moment release
KW  - fluid injection
KW  - stick slip
KW  - fault creep
KW  - acoustic emission
Y1  - 2020
U6  - https://doi.org/10.1029/2020GL089576
SN  - 0094-8276
SN  - 1944-8007
VL  - 47
IS  - 22
PB  - American Geophysical Union
CY  - Washington
ER  -