The 1944 Tonankai Earthquake

Posted by Karl Lundgren on Dec 07, 2024

Imagine it’s a crisp December afternoon in 1944 on Japan’s Pacific coast. Fishermen are mending their nets by the shore, and families are preparing for another day of wartime rationing and uncertainty. The hum of daily life continues, despite the distant echoes of a world at war. Suddenly, the ground beneath them roars to life. The shaking starts gently, but within moments, it becomes violent, relentless, throwing people to the ground and collapsing buildings like sandcastles.

As the earth finally stills, a more ominous sound rises—a distant, thunderous rumble from the sea. Villagers stare in horror as the ocean retreats, exposing the seafloor, a phenomenon some recognize as a harbinger of doom. Moments later, towering walls of water crash ashore, sweeping away homes, livelihoods, and lives in their path. Chaos reigns as survivors scramble to higher ground, clinging to anything that might keep them afloat.

This was the reality for those caught in the 1944 Tonankai Earthquake, a seismic catastrophe that changed Japan forever. While it struck at a time when the nation’s focus was on war, the lessons it imparted became a blueprint for modern disaster preparedness. In the aftermath of this dual disaster—earthquake and tsunami—Japan began a journey of resilience, one that continues to shape its response to natural calamities today.

In this article, we delve into the science, the impact, and the legacy of the 1944 Tonankai Earthquake, exploring how this devastating event reshaped Japan’s approach to living on the edge of the Pacific Ring of Fire.

The 1944 Tonankai Earthquake: Japan’s Precursor to Modern Disaster Preparedness

The 1944 Tonankai Earthquake was one of the most devastating seismic events in Japan’s history, leaving an indelible mark on the nation’s approach to disaster management. Striking central Japan on December 7, 1944, the earthquake measured an estimated 8.1 on the moment magnitude scale and was followed by a destructive tsunami that compounded the devastation. This disaster unfolded during World War II, further complicating the response and recovery efforts. It became a critical turning point for Japan, highlighting the vulnerabilities of a country located on the Pacific Ring of Fire and laying the groundwork for more robust disaster preparedness measures.

Geological Background of the Tonankai Earthquake

The Tonankai Earthquake occurred along the Nankai Trough, a subduction zone where the Philippine Sea Plate sinks beneath the Eurasian Plate. This region has a history of producing massive earthquakes, often referred to as “megathrust” earthquakes due to the immense energy they release.

The Nankai Trough is part of a complex tectonic system that includes several fault lines and subduction zones, making it one of the most seismically active regions in the world. The 1944 event was triggered by a rupture along a segment of the Nankai Trough, causing the seafloor to shift and displace massive volumes of water, which in turn generated a tsunami.

The earthquake's hypocenter was located off the Kii Peninsula at a depth of approximately 30 kilometers (18.6 miles). This offshore location amplified the tsunami's impact, particularly along the Pacific coastline of Honshu.

The Immediate Impact

Ground Shaking

The earthquake struck at 1:35 PM local time, causing intense shaking that lasted several minutes. Buildings in towns and cities such as Nagoya, Shizuoka, and Wakayama were severely damaged. Many structures, built using traditional wooden methods, collapsed under the prolonged and violent tremors. The urban infrastructure of the time was ill-equipped to withstand such a seismic event.

Tsunami

The tsunami waves reached heights of up to 10 meters (33 feet) in some areas, inundating coastal towns and villages. The tsunami was responsible for a significant portion of the death toll and destruction, sweeping away homes, roads, and anything else in its path. Low-lying areas bore the brunt of the devastation, with entire communities obliterated.

Casualties and Damage

The disaster claimed an estimated 1,223 lives, although the true death toll may have been higher due to incomplete records from wartime Japan. Tens of thousands of homes were destroyed, and agricultural lands were rendered unusable due to saltwater intrusion. Economic losses were immense, but precise figures are difficult to ascertain due to the chaos of the war.

The Historical Context: Wartime Challenges

The Tonankai Earthquake occurred during World War II, a period when Japan’s resources were heavily allocated to its military campaigns. The nation was already under severe strain, dealing with rationing, bombings, and widespread hardship.

The earthquake added another layer of suffering to an already beleaguered population. The government’s response was hampered by wartime priorities, which limited the availability of manpower, materials, and organizational capacity for disaster relief. Recovery efforts were further complicated by censorship, as the government sought to minimize reports of the disaster to maintain morale and avoid giving strategic information to enemy forces.

Lessons Learned and Evolution of Disaster Preparedness

The 1944 Tonankai Earthquake was a wake-up call for Japan, exposing the inadequacies of its disaster response systems and the vulnerabilities of its coastal communities. While immediate changes were limited due to the war, the event influenced long-term policies and attitudes toward disaster management.

Improved Earthquake Research

In the aftermath of the earthquake, Japanese scientists began to study seismic activity along the Nankai Trough more intensively. This research laid the foundation for modern seismology in Japan, contributing to the understanding of tectonic activity and the potential for future megathrust earthquakes.

Building Codes and Infrastructure

One of the key takeaways from the Tonankai Earthquake was the importance of earthquake-resistant construction. After the war,

Japan implemented stricter building codes designed to improve the resilience of structures against seismic forces. These measures have been continually updated, with major advancements following subsequent earthquakes, such as the 1995 Kobe Earthquake.

Tsunami Awareness and Mitigation

The destructive tsunami underscored the need for better early warning systems and coastal defenses. In later decades, Japan invested heavily in tsunami walls, evacuation routes, and public education campaigns to reduce the risk to coastal populations.

Disaster Preparedness Culture

The earthquake also contributed to the development of Japan’s culture of disaster preparedness. Regular drills, public awareness campaigns, and a focus on community-level response planning became integral to minimizing the impact of future disasters.

Modern Implications: The Legacy of Tonankai

The Tonankai Earthquake is often viewed as a precursor to subsequent disasters along the Nankai Trough, including the 1946 Nankaido Earthquake and the 2011 Tohoku Earthquake and Tsunami. Each event has reinforced the lessons learned from the 1944 disaster, driving further advancements in technology, policy, and public awareness.

Seismic Monitoring

Japan now boasts one of the most advanced seismic monitoring systems in the world, with networks of sensors providing real-time data to predict and respond to earthquakes. This system includes the Japan Meteorological Agency's Earthquake Early Warning (EEW) system, which alerts the public seconds to minutes before strong shaking begins.

Tsunami Warning Systems

The tsunami generated by the 1944 earthquake highlighted the need for timely alerts. Today, Japan operates sophisticated tsunami warning systems that use seismic data to forecast wave heights and arrival times, giving coastal residents precious time to evacuate.

Urban Planning

Modern urban planning in Japan incorporates lessons from the Tonankai Earthquake, with an emphasis on designing cities to withstand both seismic shaking and tsunami inundation. This includes the strategic placement of evacuation centers and the construction of multi-use facilities that can serve as shelters during disasters.

Conclusion: A Disaster That Shaped Japan’s Future

The 1944 Tonankai Earthquake was a tragic event that tested Japan’s resilience during one of its most challenging periods. The disaster not only claimed lives and caused widespread destruction but also exposed critical weaknesses in the nation’s disaster preparedness. In the decades that followed, Japan transformed its approach to managing natural disasters, becoming a global leader in earthquake and tsunami mitigation.

As we reflect on the Tonankai Earthquake, it serves as a reminder of the importance of learning from past events to build a safer future. For Japan, this means continuing to innovate, educate, and prepare for the inevitable seismic challenges that lie ahead. For the world, the Tonankai Earthquake offers valuable lessons in resilience, adaptability, and the enduring human spirit.

So what can we do to get better prepared?

HAVE AN EARTHQUAKE KIT

A kit is not a safety blanket you just purchase to make yourself feel better, it is an important investment in your household’s safety and preparedness. Not all emergency kits are created equal, and we highly recommend using the Province of BC and Government of Canada resources when building or buying a kit. We are also pleased to offer Earthquake Kits that developed to meet the government requirements for emergency preparedness. Visit our Gov BC Earthquake Kit product page to view the contents of our kits and feel free to use this as a guideline for assembling your own. What’s important to us is not that you buy a kit from us, but that every household have a kit at the ready in case something unexpected should occur.

EXPAND THE EARLY DETECTION & WARNING SYSTEM IN BC

The Province of BC and the Federal Government have made huge strides in this area in recent years implementing an Emergency Notifications network through mobile carriers and testing it to great success levels. This can provide seconds to even minutes of advanced notice prior to an earthquake being felt in any given location. However, a network of this complexity relies on strategically positioned censors along the coastline. We need to continue expanding this network of sensors and make sure that existing censors are being properly monitored and maintained.

We also need to expand from mobile phone notifications to physical alarms in homes, buildings, and especially schools/daycares.

For more details on how this Early Detection Grid works, please check out the following video by the CBC several years ago.