Numerical Simulations of Tsunamis Triggered by Puysegur Subduction Zone Earthquakes and Their Impact in Aotearoa New Zealand

This study focuses on past and potential tsunamis generated by the Puysegur Subduction Zone, located southwest of Aotearoa New Zealand. Numerical modelling of historical events, including the tsunami of 25 March 2025, the Dusky Sound tsunami of 15 July 2009, and a tsunami triggered by a hypothetical Mw 8.9 earthquake scenario, is performed to establish the capacity of these tsunamis to impact the Fiordland region and its neighbourhood. The results notably indicate that strong site effects occur in the Fiordland region, where the confined fjord geometry locally amplifies wave heights (with a factor of 2 and sometimes more) and prolongs oscillations in very specific locations. The hypothetical scenario produces very strong currents exceeding 30 m/s in shallow areas and inside inlets and fjords. Such dynamics, often underestimated, can be felt even with moderate wave amplitudes like the Dusky Sound tsunami. Lastly, the study highlights a severe deficit of instrumental records and the need to improve monitoring and research in this under studied area.