The 2023 Kahramanmaraş, Turkey, earthquake sequence surface ruptures modified multi-earthquake cycle fault damage and spring hydrology

Alexis K. Ault, Sinan O. Akciz, Dennis L. Newell, Musa Balkaya, Alexandra A. DiMonte, Greg Hirth, & Cengiz Zabcı

Submitted September 10, 2023, SCEC Contribution #13144, 2023 SCEC Annual Meeting Poster #130

How do the mechanical, thermochemical, and hydrologic properties of near-surface fault rocks sustain or arrest earthquake ruptures? Addressing this question informs insitu earthquake rupture processes and controls on strong ground motions. New mapping together with rock and fluid samples of the 6 February 2023 Kahramanmaraş, Turkey, earthquake sequence ruptures provide an opportunity to benchmark near-surface fault properties to uniquely seismic slip rates and characterize fluid geochemistry and CO2 flux in the aftermath of large magnitude events.

The Mw 7.8 and 7.5 earthquakes produced complex surface rupture patterns, fissures, and scarps where they crossed regions of high topography in the NE terminus of the left-lateral East Anatolian fault and the Çardak fault. New fieldwork focused on the Mw 7.5 Elbistan earthquake that bilaterally ruptured along the Çardak fault and onto the newly identified Çıḡlık fault. The rupture created fragile, m-scale, scarps with cm-spaced, planar to arcuate, strike- and oblique-slip slickenlines. It also produced new bubbling springs; new and existing springs have high dissolved CO2 with variable total dissolved solids. CO2 flux measurements are elevated along the ruptures with the highest fluxes at the location of highest observed displacement.

Along the mature Çardak fault, the rupture exploits meters-wide zones of fault gouge and damage created by past earthquake cycles. Gouge composition includes clay, serpentinite, phyllite, carbonate, and mixtures of these lithologies. Heterogeneous clay-rich gouge has a black, aphanitic groundmass studded with mm-diameter phacoids and networks of undulous, glossy, sub-mm-thick slip surfaces. New scanning electron microscopy, energy dispersive spectroscopy, and Raman spectroscopy of these slip surfaces show they comprise C-rich ultracataclasite overlain by foliated clay nanoparticles, which develop at seismic slip rates in laboratory experiments. Exposures of the rupture interface ~1-3 m below the ground surface reveal it comprises poorly-consolidated ultracataclasite or foliated, glassy clay. Ongoing multi-scale characterization of gouge and rupture interface samples, together with spring water and gas chemistry, will inform their coupled mechanical and hydrological evolution during this earthquake cycle. These collective data can inform how multi-earthquake cycle materials may localize slip during a future large magnitude earthquake along the southern San Andreas fault.

Key Words
Turkey earthquakes, Çardak fault, on-fault damage, clay gouge, springs, CO2 flux

Citation
Ault, A. K., Akciz, S. O., Newell, D. L., Balkaya, M., DiMonte, A. A., Hirth, G., & Zabcı, C. (2023, 09). The 2023 Kahramanmaraş, Turkey, earthquake sequence surface ruptures modified multi-earthquake cycle fault damage and spring hydrology. Poster Presentation at 2023 SCEC Annual Meeting.

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