Detailed imaging of accretionary wedges reveal complex splay fault networks which could pose a significant tsunami hazard. However, the dynamics of multiple splay fault activation and interaction during megathrust events and consequent effects on tsunami generation are not well understood.
We use a 2D dynamic rupture model with six complex splay fault geometries consistent with initial stress and strength conditions constrained by a geodynamic seismic cycle model. The dynamic seafloor displacements serve as input for a 1D shallow water tsunami propagation and inundation model.
We find that all splay faults rupture coseismically due to either slip on the megathrust, dynamic stress transfer, or stress changes induced by seismic waves. The ensuing tsunami features one high-amplitude crest related to rupture on the longest splay fault and a second, broader wave packet resulting from slip on the other faults. This results in two episodes of flooding and 77% larger run-up length.