Surface CO2 flux tracks rupture-dependent healing along continental strike-slip faults

Alexis K. Ault, Dennis L. Newell, Musa Balkaya, Sinan O. Akciz, Srisharan Shreedharan, & Greg Hirth

Submitted August 30, 2026, SCEC Contribution #15274, 2026 SCEC Annual Meeting Poster #TBD

Faults must heal between earthquakes to rupture again, in part by sealing the fracture networks that each rupture creates. Laboratory experiments document time-dependent permeability reduction in fault zone materials, but spatially and temporally resolved field observations of this healing process are rare. Here we present two years of surface CO2 flux measurements, ~1100 in total, spanning 100 km of the 2023 MW 7.6 Elbistan earthquake rupture in Türkiye. Biogenic CO2 flux, a proxy for near-surface gas permeability, is elevated (up to 230 g m-2 d-1 six months after rupture) exclusively at the bedrock-hosted rupture trace, falling to background within a meter, and initial flux scales with coseismic offset. Background flux off the rupture is time-invariant, even where geodesy documents kilometers-wide off-fault deformation, implying that off-fault permeability healed within six months or never reached the connectivity required for gas transport. Rupture flux declined by more than an order of magnitude following a power law, consistent with progressive closure of earthquake-generated cracks. Where shallow, stress-driven afterslip was concentrated, flux declined more gradually, indicating ongoing creep perturbs healing. These results demonstrate that near-surface fault healing along large continental strike-slip fault systems, like the San Andreas fault, is paced by coseismic rupture behavior and post-seismic deformation, revealing an along-strike variability in healing that current earthquake cycle models do not capture.

Citation
Ault, A. K., Newell, D. L., Balkaya, M., Akciz, S. O., Shreedharan, S., & Hirth, G. (2026, 08). Surface CO2 flux tracks rupture-dependent healing along continental strike-slip faults. Poster Presentation at 2026 SCEC Annual Meeting.

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