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Frictional behaviors of the serpentine-rich East Anatolian Fault Rocks collected from the 2014 Kartal trench site

Hiroko Kitajima, Rodrigo Gomila, Telemaco Tesei, Marco Favero, Giulio Di Toro, Hisao Kondo, Selim Özalp, Hasan Elmaci, & Ersin Özdemir

Submitted September 10, 2023, SCEC Contribution #13207, 2023 SCEC Annual Meeting Poster #112

The East Anatolian Fault (EAF) is one of the major strike-slip faults and has hosted devastating earthquakes including the Mw 7.8 earthquake in February 2023. Despite significant earthquake hazard risks, frictional properties of the EAF rocks have not been documented. Here, we report the preliminary results of friction experiments conducted on the serpentine-rich fault breccia of EAF. The samples were collected in 2014 from a trench site on the main EAF in Kartal village, located about 25 km east of Kahramanmaraş [Kondo et al., 2023]. The trench site is also nearby a junction between the EAF (strike of N75E) and the Narli segment of the Dead Sea Fault Zone (strike of ~N20E) [Emre et al., 2013; 2018]. The rupture of 2023 Mw 7.8 earthquake was initiated and propagated ~20 km northward along the Narli segment and then jumped to the EAF [e.g., Melger et al., 2023; Okuwaki et al., 2023]. The friction experiments were conducted on disaggregated samples (<106 micron), which are composed of mainly serpentine but also contain smectite, using the hydrothermal rotary-shear friction apparatus at the University of Padova. The samples were sheared at a constant effective normal stress of 10 MPa, temperatures ranging from 25 to 300ºC, and sliding velocities ranging from 0.007 – 7 micron/s, and both velocity-step experiments and slide-hold-slide tests were conducted. The friction coefficient increases with temperature; it is 0.28 – 0.33 at room temperature, 0.38-0.42 at 100ºC, 0.45-0.52 at 150ºC, 0.48-0.55 at 225ºC, and 0.35-0.55 at 300ºC. Velocity-weakening behavior is observed at room temperature with the velocity-dependence parameter (a-b) ranging from -0.001 to -0004, and it is shifted to velocity-neutral behavior at 100ºC and velocity-strengthening behavior above 150ºC with a-b ranging from 0.001 to 0.010. The slide-hold-slide experiment shows no healing and the amount of reduction in friction coefficient during holds increases with not only hold time but also temperature. Our results imply that relatively low friction values and velocity-weakening behaviors of serpentine-rich faut rocks near the surface may influence the complicated rupture processes of the 2023 Mw 7.8 earthquake, including the bilateral and multi-segment rupture propagation on the main East Anatolian Fault from the junction with the Narli segment as well as supershear ruptures [e.g., Melger et al., 2023; Okuwaki et al., 2023; Delouis et al., 2023].

Key Words
friction, East Anatolian Fault

Kitajima, H., Gomila, R., Tesei, T., Favero, M., Di Toro, G., Kondo, H., Özalp, S., Elmaci, H., & Özdemir, E. (2023, 09). Frictional behaviors of the serpentine-rich East Anatolian Fault Rocks collected from the 2014 Kartal trench site. Poster Presentation at 2023 SCEC Annual Meeting.

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