Quantifying Off-Fault Plastic Strain in 3D Dynamic Rupture Models: Insights from the 2023 Kahramanmaraş Earthquake

The 2023 Turkey earthquake sequence generated widespread off-fault deformation. Recent 3D InSAR analyses of the doublet sequence show that ~35% of coseismic slip was accommodated by off-fault deformation extending up to 5 – 7 km from the fault (Liu et al., 2025). These observations, coined Absent Surface Displacement (ASD), may highlight the complex interplay between off-fault deformation, geometric fault complexity, and near-surface off-fault material properties. Quantifying how such deformation patterns emerge, and whether numerical earthquake models can capture their spatial organisation, remains an open question. 

In this study, we investigate the relationship between InSAR-derived ASD patterns from the MW 7.8 Kahramanmaraş rupture and synthetic off-fault plastic strain fields, which represent distributed inelastic yielding of the surrounding medium under dynamic rupture loading. This is generated in a suite of six different 3D dynamic rupture simulations with non-associative off-fault Drucker-Prager plasticity. These models extend on those presented in Gabriel et al. (2023) and incorporate varying on-fault frictional and structural complexities, such as fault roughness or fault waviness, variable fracture energy through different frictional parameters, and supershear initiation rupture speeds. We analyse fault-normal profiles along the geometrically complex rupture trace, and explore approaches for quantifying along-strike variability in inelastic yielding regions, plastic strain distribution and deformation asymmetry. Our analysis focuses on exploring whether off-fault plasticity can serve as a proxy for ASD and how geometric complexities and different dynamic rupture model ingredients influence the distribution and magnitude of off-fault deformation. This work provides an initial step toward constraining the consistency between observed and modelled near-fault deformation, and toward improving the representation of off-fault processes in physics-based earthquake rupture simulations.