The 2025 Kamchatka Tsunami Event: Warning Performance, Field Survey, and New Applied Methodologies for Pacific Islands.

The Mw 8.8 earthquake near the Kamchatka Islands triggered a Pacific-wide tsunami alert, leading to the activation of regional and national tsunami warning systems and emergency response procedures, including in French Polynesia and its 118 islands with three different warning levels. This event offers a unique opportunity to evaluate tsunami warning performance, observational capabilities, and hazard assessment strategies for Pacific Island environments.

This contribution presents a feedback from the tsunami alert and warning process during the Kamchatka event, with a focus on the early detection, source characterization, alert issuance timeline, and consistency between forecasted tsunami parameters and observed signals available in realtime and post-event observations.

These tsunami observations from coastal tide gauges, deep-ocean pressure sensors, and post-event field surveys conducted in French Polynesia are analyzed to document wave properties, arrival times, and local amplification effects but also evaluate model performance, particularly regarding the persistence of hazardous sea-level oscillations and the estimation of the end of warning.

Special emphasis is placed on the presentation of this new forecasting tool used for the first time in the warning context with its capability to forecast the estimation of the end of warning. The tools are developed by the Centre Polynésien de Prévention des Tsunamis (CPPT), the French Polynesian Tsunami Warning Center, which has been operational for more than 60 years. This methodology is based on an early robust source characterization that allow to perform a global numerical modeling to evaluate the potential tsunami impact for more than 24 hours after the first arrival time in complex island and atoll environments.

The study also identified gaps and objectives that still remains about early tsunami source evaluation and also the need to rebuild and update the tsunami hazard assessments for Pacific Island territories using a global probabilistic approach, highlighting key challenges such as limited bathymetry knowledge, limited historical data, sparse instrumentation, and strong site-specific effects.

Lessons learned from the Kamchatka Mw 8.8 tsunami emphasize the importance of combining communities and operational warning feedback, field observations, and methodological innovation to enhance tsunami preparedness and resilience in the Pacific.