Links between fault mineralogy, fabric, friction, and rupture behavior of the Mw 7.6 Elbistan earthquake, Türkiye

Leslie Garcia, Alexis K. Ault, Alba M. Rodriguez Padilla, Musa Balkaya, Caden J. Howlett, Srisharan Shreedharan, Dennis L. Newell, Sinan O. Akciz, Cengiz Zabcı, & Greg Hirth

Submitted September 7, 2025, SCEC Contribution #14380, 2025 SCEC Annual Meeting Poster #TBD

Shallow (<1 km) fault material properties impact earthquake rupture propagation, seismic wave radiation, and near-field ground shaking. Yet, the relationships among fault zone composition, fabric development, and frictional behavior, and how they shape the rupture patterns of large earthquakes, are poorly constrained. We address this gap using a one-of-a-kind sample set and observations acquired immediately after the 6 February 2023 Mw 7.6 Elbistan earthquake in Türkiye. This event caused a bilateral rupture of the Çardak fault, extending ~150 km to the Yeşilyurt fault.

We integrate detailed field data, rupture zone mineralogy from X-ray diffraction, and preliminary results from frictional experiments on rupture interface samples from nine sites along ~95 km of the rupture. We complement these observables with independently acquired metrics of surface rupture characteristics (e.g., number of strands, length, displacement measurements). The rupture, including along the Yeşilyurt fault, exploited both pre-existing fault gouge and strongly foliated bedrock. Segments flanking the epicenter had past Holocene ruptures overprinted by the Mw 7.6 event. Near to and west of the epicenter, where previous studies reported supershear rupture propagation, the rupture is localized to a single strand with measured offsets of 6-8.5 m. Here, the rupture interface is dominated by weak phases like smectite that are locally present in the broader Çardak fault zone and a well-developed, highly localized shear fabric that was comminuted by fault slip. The site of maximum offset (~8.5 m) corresponds to a bi-material interface composed of altered serpentinite and sheared carbonate. Locations where the rupture partitions into multiple strands exhibit correspondingly lower displacements, increased off-fault deformation, and lower (<30%) smectite content.

These observations suggest rupture localization, high displacement, and supershear velocities may have been facilitated by a combination of weak phases and a well-developed fabric characteristic of the mature Çardak fault. Ongoing low-velocity deformation experiments will quantify frictional behavior of these rupture materials, ultimately linking fault zone lithologic and structural heterogeneity to large surface ruptures on continental transforms, such as the San Andreas fault system.

Key Words
Türkiye, surface rupture, rheology, fault zone characterization

Citation
Garcia, L., Ault, A. K., Rodriguez Padilla, A. M., Balkaya, M., Howlett, C. J., Shreedharan, S., Newell, D. L., Akciz, S. O., Zabcı, C., & Hirth, G. (2025, 09). Links between fault mineralogy, fabric, friction, and rupture behavior of the Mw 7.6 Elbistan earthquake, Türkiye. Poster Presentation at 2025 SCEC Annual Meeting.

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