The Imminent Threat of the Nankai Trough Earthquake: A Comprehensive Analysis

Introduction: The Looming Crisis of a Nankai Trough Mega-Earthquake

The Nankai Trough mega-earthquake poses a significant threat of catastrophic damage to the Japanese archipelago. The probability of its occurrence is high, estimated at 70-80% within the next 30 years. The projected impact includes seismic intensity 7 tremors across a vast region from Shizuoka to Miyazaki prefectures, coupled with the possibility of tsunamis reaching up to 30 meters in height along the Pacific coast. With an estimated death toll of up to 320,000, this unprecedented disaster could jeopardize the very existence of the nation.

Understanding the Nankai Trough

The Nankai Trough is the boundary where the Philippine Sea Plate subducts beneath the Eurasian Plate, located on the seabed stretching from off the coast of Shikoku to Suruga Bay. This plate boundary has repeatedly experienced massive earthquakes in the past, with a recurrence interval of approximately 100-200 years. The last Nankai Trough mega-earthquakes, the 1944 Tonankai earthquake and the 1946 Nankai earthquake, occurred over 70 years ago, suggesting that the next mega-earthquake is imminent.

Estimated Damage from a Nankai Trough Mega-Earthquake

In the event of a Nankai Trough mega-earthquake, the following damages are anticipated:

Earthquake Shaking and Damage

Seismic intensity 7 tremors are expected in some areas from Shizuoka to Miyazaki prefectures, potentially causing building collapses and landslides.
Strong tremors of seismic intensity 6+ to 6- are expected over a wide area, potentially causing numerous injuries due to falling furniture and objects.
Long-period ground motions may cause significant swaying and damage to high-rise buildings and long bridges.

Tsunami Damage

Tsunamis reaching up to 30 meters in height may strike the Pacific coast, causing devastating damage to coastal urban areas and port facilities.
Tsunamis may inundate inland areas, submerging houses and infrastructure over a wide area.
Many residents may be unable to evacuate due to tsunami inundation or isolation, resulting in a high number of casualties.

Compound Damage

The combined effects of earthquakes and tsunamis may cause prolonged disruptions to lifelines (electricity, gas, water, and communication).
Prolonged evacuation may lead to severe issues such as food and supply shortages and deteriorating sanitation.
In addition to direct damage from earthquakes and tsunamis, indirect impacts such as economic stagnation and social unrest may also be significant.

Countermeasures for the Nankai Trough Earthquake

Various countermeasures are being implemented to address the Nankai Trough mega-earthquake:

Hard Countermeasures

Construction of seawalls and tsunami evacuation towers
Promotion of seismic retrofitting and building reconstruction
Securing emergency transportation routes and evacuation routes

Soft Countermeasures

Creation and dissemination of hazard maps
Conducting evacuation drills and raising disaster awareness
Utilization of Earthquake Early Warning and tsunami warnings

Self-Help and Mutual Aid Initiatives

Promotion of individual disaster preparedness measures such as stockpiling supplies and securing furniture at home
Encouraging community-based disaster prevention activities
Strengthening disaster preparedness systems in companies and schools

Examples of Regional Initiatives

Kochi Prefecture

Actively constructing tsunami evacuation towers and securing evacuation routes
Regularly holding disaster prevention drills and workshops for residents to raise awareness
Utilizing ICT technologies for disaster prevention, such as developing disaster prevention apps and disseminating information through social media

Shizuoka Prefecture

Has been promoting its own disaster prevention measures for the Tokai earthquake for many years, and residents are said to have a high level of disaster awareness
Actively conducting tsunami evacuation drills and disaster prevention education to create an environment where each resident can proactively engage in disaster prevention
Collaborating with companies to develop disaster prevention products and fostering disaster prevention volunteers, among other initiatives involving various stakeholders

Wakayama Prefecture

Promoting the relocation of residents from tsunami inundation zones and collective relocation to higher ground
Fostering the development of disaster prevention leaders and strengthening disaster prevention organizations to enable residents to proactively engage in disaster prevention activities
Enhancing disaster prevention education and strengthening the dissemination of disaster prevention information

Conclusion: Enhancing Individual Disaster Awareness and Preparedness

The Nankai Trough mega-earthquake, if it occurs, is expected to cause tremendous damage to the Japanese archipelago. However, by raising our individual disaster awareness and preparing in advance, we can mitigate the damage.

Check hazard maps to understand the risks at your home and workplace
Identify evacuation routes and shelters and share them with family and friends
Stockpile emergency food and supplies and check them regularly
Simulate actions to take in the event of an earthquake or tsunami to be prepared

The Nankai Trough mega-earthquake is not someone else’s problem. Raising disaster awareness and engaging in community-based disaster prevention efforts are crucial for ensuring future safety and security. Our individual actions have the power to shape the future.

References

Cabinet Office “Information on the Nankai Trough Earthquake”
Japan Meteorological Agency “About the Nankai Trough Earthquake”
Earthquake Research Committee “Long-term Evaluation of Earthquake Activities in the Nankai Trough”

The Imminent Threat of the Nankai Trough Earthquake: A Comprehensive Analysis