Overview

• The Earthquake Research Committee published dual 30-year estimates for a magnitude-8+ Nankai Trough event at 60%–90% or higher and 20%–50%, replacing January’s single figure of about 80%.
• The threat remains in the highest likelihood category (III-rank), and the assumed source region and government damage scenarios are unchanged.
• The higher range stems from a time-prediction model that incorporates Muroto Port uplift records with updated error handling, while the lower range relies only on average recurrence intervals.
• Committee chair Naoto Hirata said the situation warrants immediate earthquake and tsunami preparedness, noting roughly 80 years have passed since the Showa-era Nankai event.
• The panel says it will stress the higher estimate in public messaging, as disaster-information experts urge clearer guidance that turns probabilities into concrete protective actions.