Consideration of rupture kinematics increases tsunami amplitudes in far-field hazards assessments

Tsunami hazard assessments often assume that co-seismic crustal deformation occurs instantaneously, particularly in probabilistic tsunami hazard analyses (PTHA). However, this simplification neglects the kinematics of rupture propagation, which may influence tsunami amplitudes at distant sites. Building on previous work, this study investigates the impact of rupture kinematics – specifically rupture directivity and duration – on far-field tsunami amplitudes. Using 2600 synthetic megathrust earthquake scenarios along a 1500 km segment of the Alaskan subduction zone, I model tsunami propagation with both instantaneous and time-dependent rupture assumptions. Simulations reveal that source kinematics can significantly rotate the tsunami radiation pattern and increase peak amplitudes by over 30% at far-field sites for large (Mw>9.0) events. When incorporated into a full PTHA framework, the inclusion of rupture kinematics systematically increases hazard estimates at most coastal locations. These results suggest that neglecting rupture kinematics may lead to underestimation of far-field tsunami hazard, particularly for large, unilateral ruptures. I recommend the formal inclusion of rupture kinematics in both deterministic scenario design and probabilistic hazard frameworks to better capture the full range of potential tsunami impacts.