Abstract: [Objective]Why splay faults in continental transform fault systems rupture preferentially during strike-slip earthquakes remains an open question. Deciphering the underlying mechanism could enhance the understanding of earthquake physics and seismic hazards.[Methods]In this approach, with the faults regarded as the frictional contact between two blocks, we employ the stress-strain conditions obtained from quasi-static simulations as initial conditions for dynamic rupture simulations and the sudden transitioning from static to dynamic friction. The region of maximum slip obtained in the first step of the simulation corresponds to the area of minimum static friction in the quasi-static model, which indicates the nucleation zone of the earthquake. Simultaneously, we examine the key factors influencing the nucleation sites of the 2023 Mw 7.8 Kahramanmara? earthquake using a simplified 3D elastic-plastic model. [Results]The results show that the proposed earthquake nucleation simulation method has high accuracy, and reveal that the mechanical coupling between the splay Nurda?? Fault (NF) and the main fault exhibits nonlinear behavior due to changes in the geometric structure of the NF. The pronounced deflection of the NF, especially along the depth, would significantly accelerate the earthquake nucleation and lead to the shift of the nucleation position on the NF.[Conclusion]In this study, we address the problem of high degrees of freedom in finite element models during the process of balancing static rock pressure (pre-stress) and gravitational effects, improving the accuracy of the dynamic simulation. And our physical-based simulation successfully reproduces the coseismic slip pattern derived by the kinematic finite fault inversion. This study provides a plausible explanation for why large strike-slip faults begin on splay faults.