An Analysis of the Potential Impact of the Nankai Trough Megaquake on Japan's Prefectures

Main Content

An Analysis of the Potential Impact of the Nankai Trough Megaquake on Japan's Prefectures

---

1. Introduction

The Nankai Trough earthquake refers to a large-scale subduction zone earthquake that could occur off the southern coast of Japan’s main island, Honshu. According to long-term assessments by Japan’s governmental Earthquake Research Committee, there is over a 70% probability of such an earthquake, potentially magnitude 8-9, occurring within the next 30 years. The resulting strong ground shaking and tsunami could affect large areas across western and central Japan.

---

2. Overview of the Affected Areas

The estimated affected regions include:

• Tokai region (e.g., Shizuoka, Aichi)
• Kinki/Kansai region (e.g., Osaka, Kyoto, Hyogo)
• Chugoku region (e.g., Hiroshima, Okayama)
• Shikoku region (e.g., Kochi, Tokushima, Ehime)
• Northern Kyushu (e.g., Fukuoka, Oita)

The impact will vary by area depending on seismic intensity, tsunami height, population density, and infrastructure resilience.

---

3. Regional Impact Analysis

1. Kochi Prefecture (Shikoku)

• Expected Seismic Intensity: Maximum level 7
• Tsunami Height: Over 30 meters possible
• Risk: Highly populated coastal areas with limited evacuation time; highest projected fatalities
• Challenges: Weak disaster infrastructure; mountainous terrain

2. Shizuoka Prefecture (Tokai)

• Expected Intensity: Upper 6
• Risk: Potential disruption of the Tokaido Shinkansen and key industrial corridors
• Economic Impact: Major manufacturing hub; vulnerable supply chains

3. Aichi Prefecture (Tokai)

• Expected Intensity: Upper 6 to 7
• Risk: Highly urbanized Nagoya area; risk of fire following earthquake
• Economic Impact: Headquarters of global manufacturers such as Toyota

4. Osaka Prefecture (Kinki)

• Expected Intensity: Lower 6 to Upper 6
• Risk: Tsunami may affect Osaka Bay; aging infrastructure
• Social Impact: Dense urban zones; retrofitting needed for bridges and overpasses

5. Kyoto Prefecture (Kinki)

• Expected Intensity: Upper 5 to Lower 6
• Cultural Risk: Historic temples and cultural heritage sites at risk
• Evacuation Challenge: High tourist population; complex crowd dynamics

6. Hyogo Prefecture (Kinki)

• Expected Intensity: Lower 6
• Background: Experienced the 1995 Kobe Earthquake; some resilience in place
• Risk: Kobe Port is a critical logistics hub; national economic impact if disrupted

7. Tokushima, Ehime, and Kochi Prefectures (Shikoku)

• Common Risks: High tsunami threat, mountainous isolation, aging populations
• Response Challenges: Poor access roads; delayed emergency response likely

8. Fukuoka & Oita Prefectures (Northern Kyushu)

• Expected Intensity: 4 to Upper 5
• Risk: Relatively low direct impact; may serve as logistics and aid hubs

---

4. Indirect and Nationwide Effects

• Economic Disruption: Damage to western Japan’s industrial belt may affect global supply chains
• Population Displacement: Large-scale migration of evacuees could strain resources in unaffected areas
• Fiscal Burden: Reconstruction costs could exceed hundreds of trillions of yen

---

5. Disaster Preparedness Recommendations (Expert Perspective)

• Prioritize vertical evacuation structures in coastal zones to improve tsunami survival
• Strengthen individual evacuation support systems for elderly and mobility-impaired residents
• Ensure communities can self-sustain for at least 72 hours post-disaster
• Encourage businesses and medical institutions to create Business Continuity Plans (BCP)

---

6. Conclusion

The Nankai Trough megaquake is not just a geological threat but a systemic challenge to Japan’s infrastructure, administrative coordination, and societal resilience. Only through scientifically grounded risk assessments and cross-regional cooperation can the nation minimize human and economic losses when—not if—this disaster strikes.

---