1. Overview of the Revised Damage Estimates
On March 31, 2025, the Central Disaster Management Council under Japan’s Cabinet Office revised its damage estimates for a potential Nankai Trough megaquake. This revision comes ten years after the adoption of the “Nankai Trough Earthquake Disaster Mitigation Promotion Plan” in March 2014, reflecting advancements in disaster preparedness and incorporating new scientific findings.
The updated estimates provide detailed analyses of earthquake magnitude, probability, tsunami heights, and both human and material damage. Notably, new considerations include the impact of long-period seismic waves on high-rise buildings and challenges associated with winter evacuations.
2. Key Regional Changes
The latest revisions highlight significant updates for specific regions:
- Pacific Coastal Areas: Tsunami height projections have been revised upward in some areas, emphasizing the urgency of faster evacuation measures.
- Inland Regions: The effects of long-period seismic waves are now considered, requiring enhanced measures for high-rise buildings and critical facilities like oil refineries.
- Aging Communities: Strengthened support for elderly populations and preparations for sheltering in place have become increasingly important.
3. Changes Compared to a Decade Ago
The new estimates reveal several key differences from projections made ten years ago:
- Seismic Activity: Advances in seismology have improved the accuracy of ground motion predictions, enabling more realistic damage assessments.
- Tsunamis: Improved simulation technologies and historical earthquake data have refined predictions for tsunami heights and inundation areas.
- Human Impact: While disaster preparedness efforts have reduced potential casualties, challenges remain in supporting vulnerable populations such as the elderly and disabled.
- Economic Damage: Analyses now provide deeper insights into supply chain disruptions and business continuity risks. The importance of corporate Business Continuity Plans (BCPs) has grown significantly.
4. What We Should Do
In light of these revised damage estimates, individuals and communities must take proactive steps to prepare:
- Check Local Hazard Maps: Identify risks near your home or workplace and confirm evacuation routes and shelters.
- Stock Emergency Supplies: Prepare at least three days’ worth of food, water, medicine, flashlights, radios, and other essentials.
- Discuss Family and Community Plans: Establish evacuation plans, communication methods, and roles within your family or neighborhood.
- Participate in Disaster Drills: Familiarize yourself with evacuation procedures and improve disaster awareness through regular drills.
- Strengthen Building Safety: Conduct seismic inspections of your home and undertake necessary retrofitting to ensure structural safety.
5. Conclusion
The Nankai Trough megaquake remains an imminent threat that could strike at any time. This latest revision of damage estimates serves as a critical reminder for individuals to enhance their disaster preparedness. By taking proactive measures—both individually and collectively—we can minimize the potential impact of this catastrophic event. It is essential for governments, businesses, and residents to work together to build a more resilient society.
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