Probabilistic Tsunami Hazard Assessment and Deaggregation for the Eastern Coast of Korea

Tsunamis are low-frequency but high-consequence hazards, and following the 2004 Indian Ocean and 2011 Tohoku events, probabilistic approaches have become essential for long-term risk characterization. The East Sea (Sea of Japan) is a semi-enclosed marginal sea with numerous active submarine faults and a history of recurrent tsunami events. Major cities and industrial complexes are concentrated along Korea's eastern coast. However, probabilistic tsunami hazard assessment (PTHA) studies incorporating multiple source zones with systematic deaggregation remain limited for this region.
This study conducts a comprehensive PTHA for the entire eastern coast of Korea, integrating six seismic source zones in the East Sea. A logic-tree framework was developed to represent epistemic uncertainties, comprising 2,160 simulation branches derived from source parameters including magnitude, fault geometry, dip, and strike. These simulation branches were coupled with statistical branches representing three return periods and four Aida’s K values, yielding a total of 25,920 scenario combinations. Numerical simulations were performed using the COMCOT model with nested grids at approximately 40 m nearshore resolution. Maximum tsunami heights were used to construct exceedance probability curves based on a Poisson model. Deaggregation analysis was then applied to quantify the contributions of magnitude, source distance, and source zone to site-specific hazard levels.
Hazard analysis reveals pronounced regional disparities. Sokcho and Donghae were identified as critical locations with significantly higher projected tsunami heights. This hazard amplification is attributed to wave energy focusing induced by complex bathymetric features, specifically the Yamato Rise and the K-shaped ridge. Furthermore, deaggregation analysis reveals that fault ruptures along the central eastern margin of the East Sea (Sea of Japan) are the dominant contributors to the hazard in these regions. By systematically isolating the contributions of magnitude and source zones, this study provides a physically interpretable framework for prioritizing site-specific mitigation strategies and identifying potential dominant sources.