SCEC Award Number 21157 View PDF
Proposal Category Collaborative 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 Zachary Zega, PhD student, University of Maryland
SCEC Priorities 3f, 3d, 2c SCEC Groups FARM, Geology, SDOT
Report Due Date 03/15/2022 Date Report Submitted 03/10/2022
Project Abstract
 To understand the effect of pore fluid pressure on fault slip, we conducted friction experiments on saw-cut sandstone samples containing a thin layer of fine-grained quartz gouge. The saw-cut samples were deformed under a wide range of confining and pore fluid pressures and the fault slip along the saw-cut surface during deformation was observed. Using different combinations of confining and pore fluid pressures, we produced a spectrum of slip behaviors from dynamic, seismogenic slip to transitional slow-slips. We observed 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. This result suggests that pore fluid pressure build-up may cause a transition in slip behaviors. Pore fluid pressure plays an important role in faulting instabilities and earthquake cycles as well as induced seismicity. This study sheds light on the underlying mechanisms that impede the instability to produce slow slip events.
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 will provide critical constraints to the effective stress during fault propagation and slip.
Broader Impacts The experimental results address several of the scientific objectives of SCEC5. 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.

Project Publications
Exemplary Figure Figure 3. Effect of pore fluid pressure on slip behaviors. As pore fluid pressure increases, the high frequency components diminish from the slip events. (Xing et al., in preparation).