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tada について

Dr. Nakasu is a post-doctoral fellow and an adjunct lecturer at College of Population Studies, Chulalongkorn University in Thailand. He had been working at NIED (National Research Institute for Earth Science and Disaster Prevention) as a principal research fellow and ICHARM (International Centre for Water Hazard and Risk Management), PWRI (Public Works Research Institute) as a research specialist in Japan for a decade. He has conducted many disaster field surveys such as Indian Ocean Tsunami (2004), Hurricane Katrina (2005), Typhoon Ondoy and Pepeng (2009), Great East Japan Earthquake and Tsunami (2011), and Chao Phraya River Flood (2011). He also conducted abundant disaster management research around the globe. He had been a project leader of the Working Group of Hydrology, the Typhoon Committee (WMO and UN/ESCAP) for nearly 3 years. He was also a visiting researcher at JICA (Japan International Cooperation Agency) and an adjunct instructor at several universities in Japan. He won a second prize for his poster presentation at the Society for Risk Analysis-Asia Conference in Taipei in 2014. He is a tsunami evacuation research committee member of the Japanese Association for Earthquake Engineering (JAEE). His research interests include the environment and comparative studies. 日本語版: 中須正

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_203 : Distant Tsunamis Triggered by Massive Earthquakes: The 1960 Chilean Earthquake and the 2004 Indian Ocean Tsunami

On the early morning of May 23, 1960, a massive earthquake, the largest ever recorded with a magnitude of 9.5, struck southern Chile. This earthquake unleashed a tsunami that swiftly crossed the Pacific Ocean, reaching the Japanese coast about 22.5 hours later. The tsunami, which surged up to 8 meters high, resulted in 139 deaths and caused the destruction or displacement of 2,830 buildings across Japan. Due to the geographical position of Chile opposite Japan, the tsunami’s impact was more pronounced upon reaching the Japanese shores. These distant tsunamis are particularly challenging to forecast since they occur without the preliminary tremors typically associated with earthquakes. Consequently, regions prone to seismic activity, particularly around the Pacific, including Hawaii, have established early warning systems.

Day_168 : Past Interview Records – PTWC (Pacific Tsunami Warning Center) in Hawaii (1)

 

In 2004, the Indian Ocean was struck by another significant earthquake, which triggered a devastating tsunami. At that time, the absence of a tsunami warning system in the Indian Ocean contributed to a staggering death toll of 300,000. The effectiveness of tsunami warnings is limited by their ability to reach extensive coastal areas promptly. Therefore, it is crucial for residents to be aware of their local environmental characteristics and rely on personal judgment and preparedness to mitigate the risks posed by tsunamis.

Day_202 : What is Inland Flooding?

When it rains heavily on a flat area, the rainwater does not drain away and accumulates on the ground. Water flows into low areas from surrounding small elevations. Drainage canals and small rivers are the first to overflow as water levels rise. Floods that occur in this way are called internal floods and are distinguished from external floods that occur when the levees of main rivers break or overflow. In general, internal floods include the overflows of relatively large drainage rivers that have their source in the plain and the overflows of small rivers on plateaus and hillsides into lowlands at the bottom of valleys. Floods caused by internal flooding are particularly problematic in cities and surrounding newly developed urbanized areas. What is called “urban flooding” is the flooding of urban areas, which is intensified by the structure of the city and creates new types of damage, such as the inundation of underground malls.

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

Day_200 : High-Speed Tsunamis and Delayed Warnings: The Urgency of Evacuation during the 1896 Meiji Sanriku, 1933 Showa Sanriku, and 2011 Great East Japan Earthquake and Tsunamis

Large tsunamis are caused by major earthquakes of magnitude 8 or greater. In particular, such earthquakes frequently occur along the Pacific coast of Hokkaido and Tohoku in Japan. The Sanriku coast in this region has a special shape called a “rias coast,” which is prone to tsunamis. In the 1896 Meiji Sanriku tsunami, the tsunami reached a height of 38 meters and killed about 22,000 people. Thirty-seven years later, in 1933, another major tsunami, the Showa Sanriku tsunami, struck the region, killing approximately 3,000 people. 2011’s Great East Japan Earthquake and Tsunami did not fully apply the lessons of the past, leaving approximately 18,000 people dead or missing.

The time between an earthquake and a tsunami reaching the coast is very short, from 5 to 10 minutes. Running to higher ground within this short time is almost the only way to protect yourself from a tsunami. The tsunami will reach the coast where it is the highest, and the tsunami will also reach the coast the fastest. Therefore, instead of waiting for information from the outside, it is important to have your own knowledge about tsunamis, understand your surroundings, and act on your own judgment.

Contents (in Japanese)
Source: URL:https://dil.bosai.go.jp/workshop/2006workshop/gakusyukai21.html

Day_199 : Early Signs of Geological Changes Before Landslides

Before significant landslides occur, various clear natural changes are often observed. Notable incidents include the 1963 Vajont Dam landslide in Italy and the 2006 Leyte Island landslide in the Philippines.

On the evening of October 9, 1963, a massive landslide took place near the Vajont Dam in the Alps of northern Italy. The dam, standing at 262 meters, was completed just three years prior. The landslide dislodged approximately 260 million cubic meters of earth, thrusting up the waters of the dam’s lake. The displaced water surged over the dam, rising more than 100 meters before rushing down into the valley below, resulting in approximately 2,000 fatalities. The geological layers in the area were unstable, compounded by the increased water levels from the dam. A minor landslide had previously occurred in 1960, and the landslide’s progress accelerated to several tens of centimeters per day just before the disaster. Despite ongoing monitoring, the catastrophic damage could not be prevented.

Day_140 : Natural Disasters in Europe (2) Vajont Dam Collapse

 

On February 17, 2006, a mountain 800 meters tall on the Philippine island of Leyte succumbed to a vast landslide, displacing around 20 million cubic meters of soil and claiming 1,144 lives. Before the collapse, cracks had appeared on the mountain’s ridge, and rainfall had begun to seep into the ground.

Identifying these early signs of geological change is crucial. By monitoring their progression and predicting potential danger zones, we can enhance our preparedness and safeguard our lives against such devastating natural disasters.

Contents (in Japanese)
Source: URL:https://dil.bosai.go.jp/workshop/2006workshop/gakusyukai21.html

 

What causes a landslide?

 

Day_87 : North and Central Americas – Mt. St.Helens and Mt.Pelee

1.Volcanic Disasters

North America
Mount St.Helens erupted in 1980. 57 people were dead.
St.Helens volcanic eruption was really huge. You can see this from the following video.

 

From environmental and sociological perspectives, the difference between the U.S. and Japan is the people’s and nature’s relationships. This case indicated that somehow. The people are living far from nature, on Mt.Helens. That is why the fatality number was not so large compared to the huge eruption. In Japan, people tend to live near and with nature. This is called “Satoyama” in Japanese. Other Asian countries are the same with Japan.
This will be discussed later.

Caribbean
Mount Pelee
St.Pierre City was destroyed completely in 1902 by Mt. Plee’s eruption.
The population of the city was approx. 28000; almost all were dead, only 2 survived. One of the only two survivors was in prison. The story can be seen from the following video.

2. Climate, meteorological, and hydrological disasters: Hurricanes

North America
In 1900, Galveston’s death toll was over 6,000
2005 Katrina, the death toll was over 1400, and the cost was $100 billion . UDS
In 1998, Mitch reported that 13,700 people were victimized in Honduras and 3,300 in Nicaragua
Caribbean
Hurricane Jeanne,  2800 were killed in Haiti

Disaster data, such as death toll, is sourced from the NIED DIL homepage.

Day_198 : Characteristics of Earthquake Disasters

In most cases, when a strong earthquake occurs, many people die as buildings collapse. For example, in the Kobe earthquake, more than 90% of the 5,000 people who died lost their lives within 15 minutes immediately after the quake. For this reason, it is very important to build buildings well in order to reduce the number of people who die in earthquakes. This will prevent fires, make it less likely that people will lose their homes and become permanent refugees, and reduce the problems of relief and rebuilding.

In developing countries, especially in arid and semi-arid regions, earthquakes cause many deaths. In such areas, sun-dried bricks called “adobe” are a common building material, and buildings made of these bricks often collapse easily in earthquakes, burying many people alive. In developing countries, for economic reasons, standards for making buildings earthquake-resistant are often low, and construction is often inadequate. Therefore, even earthquakes that are not that strong can easily cause serious damage. In addition, in regions with many wooden houses, such as Central America and Southeast Asia, not only can buildings collapse, but they can also catch fire.

Day_197 : The Science of Lightning: A Fascinating Force of Nature

Ever caught yourself staring at the sky, mesmerized by lightning during a storm? This natural marvel is not only captivating but also perilous. Despite centuries of study, the intricacies of lightning strikes continue to be a field of active research. In this exploration, we delve into how lightning forms, its types, associated dangers, and the science of thunder, providing insights for both enthusiasts and the casually curious.

Formation of Lightning

Lightning originates from electric charges accumulating in the atmosphere. This process begins as the sun warms the Earth, causing air to rise, cool, and form clouds. Inside these clouds, the movement of water droplets and ice particles generates an electrical charge. A significant charge difference between parts of the cloud or between the cloud and the ground can ignite a spark—lightning. The intense heat from a lightning strike causes air to expand, creating thunder.

Types of Lightning

Lightning manifests in various forms, including:

Cloud-to-Ground Lightning: The most familiar type, where a bolt strikes from the cloud to the Earth.

Intra-Cloud and Cloud-to-Cloud Lightning: Occurring within or between clouds, respectively.

Ball Lightning: A rare phenomenon of a glowing orb appearing during storms, whose origin remains a mystery.

The Thunder Phenomenon

Thunder is the sound produced by the rapid expansion of air around a lightning bolt. Timing the gap between seeing lightning and hearing thunder can estimate the distance of the strike—every five seconds equals approximately one mile.

Dispelling Lightning Myths

Contrary to popular belief, lightning can strike the same place more than once, especially if it’s a tall structure. Also, while buildings offer better protection than being outdoors, they are not entirely safe from lightning strikes.

Staying Safe During Storms

To minimize risk during thunderstorms:

Stay indoors and unplug electronics.

Seek shelter in a vehicle or sturdy building if outside.

Keep away from tall objects like trees and poles.

Spread out if in a group to reduce the risk of multiple injuries.

Tracking and Protecting Against Lightning

Modern technology, including lightning detectors and mappers, helps track and analyze lightning activity. For protection, lightning rods and surge protectors can safeguard buildings and electronics from strike-induced damages.

Lightning and Climate Change

There’s growing evidence that climate change may increase lightning frequency by creating more thunderstorm conditions. However, further research is needed to understand this relationship fully.

In Conclusion

Lightning, a compelling display of nature’s might, offers much to learn and appreciate. Understanding its science not only enhances our wonder but can also guide us in safeguarding against its dangers. So next time a storm lights up the sky, remember the fascinating science behind each bolt.

Day_138 : Natural Disasters in Europe (1)

Natural disasters in Europe mainly consist of hydrological, meteorological, climatological, earthquake and volcano eruption disasters.

europe-pic
Figure   The Europe

Earthquake disasters mainly occur in the Aegean Sea, the south-western coast of Balkan Peninsula, and the southern part of Italy. Volcanoes are active in the central and southern parts of Italy, the southern Aegean Sea, and Iceland area.

Concerning hydrological, meteorological, and climatological disasters, heavy rain and storm disasters are caused by low  pressure in the Icelandic area developed in the winter season. A cold atmospheric current coming from Arctic gains a warmer vapor stream from the Gulf Stream and develops a strong atmospheric depression in the area. This causes the strong winds and high tidal waves along the coastal areas of the North Sea.

Netherlands and England can be highlighted. The Netherlands had storm surges in 1530 and 1570. The death tolls were approximately 400,000 (1530) and 70,000 (1570) for each. The 1953 depression took an 1800-person death toll. This disaster also reached England. England’s disasters were the 1703 Thames river flood and the 2003 Heatwave. The temperature was 8–10 over the average year in August 2003.

With regard to earthquake disasters, Italy, Greece, and Portugal are the main countries to be affected.

The following past article explains the recent earthquake cases in Italy.

To be continued…