[S08] AM-1

[S08-05] Dynamic Rupture Simulation Reveals Fault Geometrical Effect on the 2023, Kahramanmaras and Ekinozu, Turkiye, Earthquake Sequence

*Ryosuke ANDO¹, Dogan Kalafat², Haluk Ozener², Esref Yalcinkaya³, Yojiro Yamamoto⁴ (1. University of Tokyo, 2. KOERI, Bogazici University, 3. Istanbul University, 4. JAMSTEC)

The 2023, M 7.8, Kahramanmaras earthquake (mainshock) occurred on February 6^th, mainly along the plate interfaces called the East Anatolia fault ruptured toward NE (accommodating the motion between Anatolia and Arabia) and the Dead Sea Fault Zone ruptured toward SW (between Arabia and Africa). Followed in 9 hours, the M 7.6, Ekinozu earthquake (largest aftershock) was hosted by the subsidiary fault system called the Cardak – Surgu faults. This earthquake sequence presents significant complexity in fault geometry and rupture patterns. The observed hypocenter indicated that the mainshock rupture nucleated away from the East Anatolia fault (EAF) and was probably located on a subsidiary fault called the N-S striking Narli fault. The Narli fault is close to the area called Maras Tripple Junction (MTJ) where Anatolian, Arabian and African plates meet. We performed a set of stress tensor inversions and dynamic rupture simulations. We used the FDP-BIEM developed by Ando, 2016, for the fully-dynamic rupture simulation. The 3-D fault geometry is built based on the previously compiled surface fault traces with constant dip angles. Based on the stress inversion using the aftershock focal mechanisms (M>4), we find that the maximum horizontal principal stress axis around the Cardak – Surgu faults is slightly rotated clockwise from that around EAF. The Narli fault and EAF are favorably oriented. The simulation can reproduce a number of coseismic features determined by seismic and geodetic observations. Such features include 1) the rupture propagated from the Narli fault to EAF; 2) initially propagated towards the northeast on EAF, and eventually to the southwest; 3) the rupture to the south is posed at a bend (MTJ) before entering into the Dead Sea Fault zone (the Amanos Fault), further delaying the southwest rupture; 4) the possible super-shear on the Amanos Fault; 5) the locations of large slip areas determined by the SAR data. Moreover, the positive dynamic Coulomb stress change (~ 2MPa) is simulated in the middle of the Cardak Fault, while the Surgu Fault experienced a smaller amplitude. These characteristics are understandable as the primary effect of the fault geometry. Acknowledgment: This work used computational resources of Earth Simulator provided by JAMSTEC through the HPCI System Research Project (Project ID: hp220105).