Rough Subducting Seafloor Reduces Interseismic Coupling and Mega‐Earthquake Occurrence: Insights From Analogue Models

The roughness of the subduction interface is thought to influence seismogenic behavior in subduction zones, but a detailed understanding of how such roughness affects the state of stress along the subduction megathrust is still debated. Here, we use seismotectonic analogue models to investigate the effect of subduction interface roughness on seismicity in subduction zones. We compared analogue earthquake source parameters and slip distributions for two roughness endmembers. Models characterized by a very rough interface have lower integrated fault strength and lower interseismic coupling than models with a smooth interface. Overall, ruptures in the rough models have smaller rupture area, duration, and mean displacement. Individual slip distributions indicate a segmentation of the subduction interface by the rough geometry. We propose that flexure of the overriding plate is one of the mechanisms that contribute to a heterogeneous stress distribution, responsible for the observed seismic behavior.Plain Language Summary The largest and most destructive earthquakes on Earth occur along the plate contact in subduction zones, the region where an oceanic plate dives below another plate. The roughness of the downgoing plate, which is a result of the seafloor topography on that plate, is thought to play a role in the occurrence of large subduction earthquakes. With analogue models that include a 3-D-printed seafloor, we test the effect of two types of seafloor roughness on the occurrence of earthquakes: a very rough versus a very smooth seafloor. We observe that the rough seafloor geometry generally hinders the occurrence of large earthquakes along the subduction interface. This finding helps us to highlight where large future earthquakes are more likely to occur.