Subduction dynamics and plate coupling along seismically active margin: the role of slab steps

The negative buoyancy of the slab drives subducting plate and trench motions, influencing tectonic stresses at convergent margins. Variations in slab depth along the trench affect plate coupling and seismicity. We investigated these effects using 3-D subduction models, focusing on slab depth variations and their impact on force balance. Results show convergence velocity is primarily controlled by slab mass and subducting plate rheology, while trench movement is sensitive to slab depth heterogeneity. The highest stress occurs around slab steps, aligning with deformation patterns observed along the Sunda margin. This study highlights the crucial role of trench-parallel forces in plate dynamics.