Rupture Dynamics and Near-Fault Ground Motion of the Mw7.8 Kahramanmaraş, Turkey earthquake of February 6, 2023

Hideo Aochi, Víctor M. Cruz-Atienza 

We studied the dynamic rupture propagation of the February 6th, 2023 (Mw7.8, 01:17 UTC) Pazarcık (Kahramanmaraş), Turkey, earthquake by incorporating the non-planar fault structure, the regional stress field, and a data-driven friction parameterization into numerical simulations. To explain the rupture extent of 200 km and the average speed, a regional non-uniform load is necessary and was determined from the orientation and intensity of the principal stresses. Careful analysis of near-fault strong motions suggests that the critical slip-weakening distance (D_c) varies smoothly along the fault strike (between 0.6 - 1.2 m) with mean value of 0.86 ± 0.34 m. Such friction and prestress heterogeneities allowed to explain local kinematic features of the rupture process imaged by Delouis et al. (2023) (e.g., two supershear rupture transients) where the fault geometry played a major role. As expected, we found clear correlation between rupture speed and radiation efficiency (η_r) along the fault, both metrics with peak values near the maximum PGAs recorded. This is the first earthquake where local heterogeneity of rupture dynamics and near-fault ground motion can be studied together so that the methodologies introduced will serve to generate comprehensive earthquake scenarios to assess the seismic hazard in other regions.