SCEC Award Number 22125 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Experimental Investigation of Effect of Pore Fluid Pressure on Stick-Slip Events
Investigator(s)
Name Organization
Wen-lu Zhu University of Maryland
Other Participants 1. Zachary Zega (PhD student);
2. potentially undergraduate students as part of their senior thesis research.
SCEC Priorities 3f, 3d, 2c SCEC Groups FARM, SDOT, Geology
Report Due Date 03/15/2023 Date Report Submitted 05/31/2023
Project Abstract
 We conducted an experimental investigation of fault slip stabilization under high pore fluid pressure conditions. In these experiments, we prepared saw-cut sandstone samples containing a thin layer of fine-grained quartz gouge. The saw-cut samples were deformed under a wide range of pressure conditions and the fault slip along the saw-cut surface was recorded during deformation. We observed a broad spectrum of slip behaviors from dynamic, seismogenic slip to transitional slow-slips. We found that at the same effective normal stress, the magnitude and duration of the stick-slip events are sensitive to the magnitude of pore fluid pressure. Increasing pore fluid pressure suppresses dynamic slip and enhances slow events. We analyzed the power spectrums of the stress drops during these slip events. The spectrograms show distinctively different frequency contents and dissipation patterns at high pore fluid pressures. The experimental results provide new insights on the link between high pore fluid pressures and slow earthquakes.
Intellectual Merit High pore fluid pressure is often detected in regions where slow slip events occur. Motivated by this close association of slow slip events with high pore fluid pressure, we propose to conduct friction experiments on saw-cut samples with a gouge layer to investigate the effect of pore fluid pressure on stick-slip. Our goal is to determine the conditions for different types of instability (i.e., stick-slip vs. slow-slip) and to quantify the effect of pore fluid pressure on slip behaviors. The experimental results shed light on how the pore fluid pressure affects fault propagation and slip.
Broader Impacts The experimental results address several of the scientific objectives of SCEC science priorities. The research project serves as a platform for training graduate and undergraduate students. The broader impacts also include 1) Full participation of women in STEM; 2) improved STEM education and educator development; 3) enhanced public engagement with science and technology through the PI and her students’ research, education and outreach activities.
Exemplary Figure Figure 3. Figure 3. Transition from stick-slip to slow slip with increasing pore fluid pressure under the same effective pressure (Pc-Pf)=70MPa. As the pore fluid pressure increases from 5 to 120 MPa, the amplitude of the stress drop during the slip events deccreases (right panel). The spectrograms show both high frequency contents diminishing under high pore fluid pressures (left panel). Unpublished experimental data, Tiange Xing and Wenlu Zhu, in preparation.