Category Archives: Fire

Great Kanto Fire Disaster 1923

The following is my past short essay for the institute after the study session on the 1923 Great Kanto Earthquake at the open office event:

In 1923, an earthquake killed over 105,000 people in the Tokyo area (including Kanagawa, where contributes approx. 30% death toll of the total). But here’s the shocking truth—87% weren’t killed by the shaking. They were killed by fire.

September 1, 1923. The earthquake struck at 11:58 AM—two minutes before noon—when families across Tokyo were cooking lunch over open flames. Within an hour, over 100 fires erupted across a city built almost entirely of wood and paper.

The fires merged into massive firestorms, generating winds so powerful they created fire tornadoes—what survivors called “dragon twists.” At the Honjo Clothing Depot, 40,000 refugees thought they’d found safety in an open field. At 4:00 PM, a fire tornado swept through. Within minutes, 38,000 people perished—over a third of the entire disaster’s death toll, in one location.

What’s tragic is that seismologist Imamura Akitsune had predicted this exact scenario 18 years earlier. He warned that cooking fires would turn an earthquake into an inferno. His senior colleague ridiculed him publicly. Imamura was right.

Japan learned. In 1960, September 1st became Disaster Prevention Day. Every Japanese child now practices earthquake drills. Gas meters have automatic seismic shut-offs. Tokyo’s wide avenues and parks? They were designed as firebreaks. The deadliest disasters aren’t always the ones we expect. Sometimes the real killer comes after.

Day_204 : The story of the Great Kanto Earthquake of 1923, which set the cities of Tokyo and Yokohama on fire

When an earthquake strikes, fires start simultaneously in many places. The combination of dispersed firefighters’ ability to extinguish fires, broken buildings and unusable roads, broken water supplies and water shortages, and congested roads with many cars makes it very difficult to extinguish fires. For these reasons, large-town fires are more likely to occur during earthquakes. This is especially true in wet areas like Japan, where buildings are mainly made of wood and fires can spread over them as they break down, causing more damage. In dry areas, many houses are made of brick or stone, which are often completely destroyed by earthquakes.

During the Great Kanto Earthquake of 1923, 320,000 houses, or about 62% of the houses in Tokyo, were burned down. There were 136 fires, 76 of which spread widely, burning as much as 44% of the city in three days. Almost all (95%) of the deaths were caused by fire. Almost the same proportion (63%) of houses burned down in Yokohama. History shows that every time there has been a major earthquake, there has also been a major fire. The basic measure against fires caused by earthquakes is to make the house earthquake-proof and prevent it from collapsing.

 

source:
https://dil.bosai.go.jp/workshop/2006workshop/gakusyukai11.html

Day_201 : Ground conditions are a fundamental factor in determining the amplification of seismic motions at the ground surface and the magnitude of earthquake damage

The condition of the ground is an important factor in determining how strongly an earthquake will be felt. For example, in the 1891 Nobi earthquake (Japan), the 1923 Kanto earthquake (Japan), and the 1985 Mexico earthquake (Mexico), the softer the ground, the stronger the earthquake shaking. Especially in softer strata, seismic waves are slower, so the shaking is greater. This shaking is further intensified when the period of the strata coincides with the period of the earthquake or building. This is called resonance and is the cause of many building failures.

For example, in the 1891 Nobi Earthquake in Japan, most houses near the epicenter were destroyed, but the number of houses destroyed decreased as one moved farther away from the epicenter. At a distance of 50 km from the epicenter, few houses were broken in areas with hard ground, while many were broken in areas with soft ground; in the 1923 Kanto earthquake in Japan, few houses were broken on the Yamanote plateau in Tokyo, while many were broken in the Arakawa lowlands; in the 1985 Mexico earthquake, the collapse of tall buildings in particular was observed, but this was also caused by soft ground.

The destruction of homes by earthquakes has a major impact on human casualties, fires, and even society as a whole. Therefore, when considering earthquake countermeasures, it is very important to carefully examine the condition of the ground.

Source URL:https://dil.bosai.go.jp/workshop/2006workshop/gakusyukai19.html