Transient Strain and Electrical Conductivity due to Fault Formation across Laboratory Stepovers

Sara Beth L. Cebry, Tamara N. Jeppson, David A. Lockner, & Eric Burdette

Submitted August 30, 2026, SCEC Contribution #15284, 2026 SCEC Annual Meeting Poster #TBD

Natural faults contain discontinuities which may have implications for earthquake hazard assessment and fluid flow. To study the effect of stepover geometry on fault activation, we prepared cylindrical Berea sandstone samples with cemented pre-existing faults (sawcut notches filled with cement paste and allowed to cure) to create a non-overlapping, extensional stepover. Pre-existing faults of uniform length were offset to create stepover distances that varied from 7.6 to 57.4 mm. When loaded under triaxial conditions, a new shear fracture formed that directly connected the pre-existing faults. Mechanical measurements showed that sample strength increased with stepover separation. Experimental mechanical measurements show that larger stepovers had increased sample strength and acted as larger barriers compared to smaller stepovers. Modeled sample stress field indicates that interactions of the preexisting faults played a major role in strength and location of the newly formed fracture. Electrical conductivity and volumetric strain measurements showed that the inelastic failure zone increased with stepover size, with good agreement between the two measurements. Permeability enhancement during failure, inferred from measured increases in electrical conductivity, also increased with stepover size. These results highlight that existing faults can interact and promote failure in otherwise unfavorable orientations, leading to the development of complex fault systems.

Key Words
fault geometry, rupture propagation, termination, permeability, resistivity

Citation
Cebry, S. L., Jeppson, T. N., Lockner, D. A., & Burdette, E. (2026, 08). Transient Strain and Electrical Conductivity due to Fault Formation across Laboratory Stepovers. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)