1991 Unzen Fugendake Volcano Eruption Killed 43 people. This disaster has taught a lot of lessons. The key words are media, volunteer firefighters, police officers, and an evacuation area. The people were all dead in the evacuation area. During the volcano eruption, media people tried to get into the area to shoot pictures, videos, and report. They went into the local people’s houses. The residents were worried about their belongings in their houses. So many volunteer firefighters (12) also went into the area to check, and police officer (2) also did that. The taxi drivers (4) bring them into the area. They all died in the area. Katia Krafft and Maurice Krafft, world’s famous French volcanologists were also dead during the disaster.
One of the most significant volcanic disasters we must know about is the 1985 Nevado del Ruiz volcano eruption. Approx.23000 citizens in Armero city were dead. The cultural aspects were embedded in this disaster. The disaster was predicted. The hazard maps indicate that the city will be affected by a volcanic eruption and lahars. Both priest and mayor told the citizens to stay in the same place because they were afraid of panic before the time, but did not tell them to evacuate. That made tragedy. The people in the city tended to follow both persons because of the culture, which is a religious and vertically structured society. There were also other factors*.
I want to introduce you to two disaster technology websites: DRH Asia-Disaster Reduction Hyperbase and Global DRR Technology.
The websites below are unavailable today (2024.12.14 confirmed); however, we can still learn the concept and idea as a significant theme.
1) DRH Asia
This site provides qualified information about DRR technology. Its content is easy to grasp, making it possible to transfer DRR technology. The content comes from many Asian countries and has been reviewed by experts. The challenge is the limited number of contents.
We can understand the quality and availability of the content.
2) Global DRR Technology This site focuses on an online Community of Practice(CoP) in Disaster Risk Reduction(DRR). Although the content is limited, the site can be easily accessed. The case study site is incredibly visually appealing.
The site below is an example of a case study site. (Figure 2)
80% ofall tsunamis occurring in the world are concentrated in the Circum-Pacific Belt.The leading countries researching the tsunami are Japan, the U.S., and Russia. The tsunami is originally a Japanese term that means a high tidal wave. The name was used by Japanese immigrants during a tidal wave caused by the 1946 Aleutian Islands earthquake (tsunami) hit in Hiro, Hawaii and it became an international word, especially an academic word, ”Tsunami”. The International Union of Geodesy and Geophysics (IUGG) is in charge of a tsunami session at the start of an international conference about tsunamis. “Tsunami” became public after the 2004 Indian Ocean Tsunami disaster.
*The word “tsunami” is composed of the Japanese words “Tsu” (which means harbor) and “Nami” (which means “wave”)(ITIC)
In 1970, a major earthquake (magnitude 7.7) in Peru caused a massive collapse of the summit of Mount Huascaran in the Andes. The large amount of rock and ice (about 100 million cubic metres) that fell from the mountain flowed down for about 14.5 kilometres at more than 300 kilometres per hour. This flow over a 230-meter-high ridge covered the town of Yungai, with a population of 25,000, in a 5-meter-thick layer, killing around 15,000 people.
Meanwhile, in Japan, a 6.8-magnitude earthquake in 1984 in western Nagano Prefecture caused the collapse of some 36 million cubic metres of earth and rock at Kiso-Ontake; in 1792, Mount Unzen-Mayuma probably collapsed in an earthquake, causing some 340 million cubic metres of rock to collapse and flow into the Ariake Sea, causing a tsunami of up to 23 metres.
In an ordinary landslide, the coefficient of friction that indicates the distance and speed at which rocks and soil move is around 0.5, but in a particularly large debris avalanche, this can drop to 0.1 and move much further and faster. Large volcanoes are more prone to such large landslides because of the instability of their internal structure.
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.
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.
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 essential to build buildings well 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 common building materials, and buildings made of these bricks often collapse easily in earthquakes, burying many people alive. In developing countries, for economic reasons, standards for building earthquake-resistant buildings are usually low, and construction is often inadequate. Therefore, even earthquakes that are not strong can easily cause severe damage. In addition, in regions with many wooden houses, such as Central America and Southeast Asia, buildings can collapse and catch fire.
The 1995 Kobe earthquake taught us a lot of lessons. Today I am going to give you the following two questions:.
1) Why were there so many early 20s victims?
2) Which floor is more dangerous, 1st or 2nd?
1) Please look at the following picture. You can see the victims’ age distribution. Females and elderlies are more likely to be victimized because of their lack of physical strength. However, why did so many people in their early 20s die? Yes, they were university students. There are many universities in Kobe. Students tended to be less rich. They tended to stay on the 1st floor in cheaper wooden apartments.
2) You already know the answer. Of course, the first floor is more dangerous, especially in a wooden house. 1981 is the year in which the Japanese government set the building code. So the buildings, apartments, etc. built after the year tended not to be destroyed by the earthquake, including the Kobe earthquake.
Photo: Dr.Takashi Inokuchi
We should learn the lessons from the disaster; this is the best thing we can do for the victims.
September 1 is Disaster Prevention Day in Japan. This is because of the 1923 Great Kanto Earthquake. This quake caused over 105,000 casualties and had huge impacts on Japanese society. The Great Kanto Earthquake is the worst disaster in Japanese history. Here, some points are picked up. First, the quake directly attacks the capital city, Tokyo. Second, the disaster killed so many people mainly by fire, not objects falling. Third, rumors made the disaster worse. Fourth, Tokyo has recovered first and strongly. With regard to the devastated areas, Tokyo and Kanagawa (Yokohama) populated areas were severely affected by the quake. The epicenter was located near Oshima Island in Sagami Bay, south of Tokyo. In Yokohama, 90 percent of all homes were damaged or destroyed. 60 percent of the city’s population became homeless (Brown University). Concerning the fire, the time at which the earthquake hit was 11:58, so the families had prepared for their lunches. Many families’ cooking stoves were overturned by the quake, causing fires. The fire spread out with strong winds. In respect of the rumors, the rumors, especially about Koreans, such as “Koreans do criminal activities and cause social confusion,” make the disaster more political. The Home Ministry declared martial law and ordered all sectional police chiefs to make maintenance of order and security top priorities. After the disaster, the radio became popular all over Japan. This is because of the disaster’s lessons. Concerning the recovery, Shinpei Goto, Mayor of Tokyo, created and proceeded with a reconstruction plan for Tokyo to rebuild better. The basic infrastructure of today’s Tokyo was built during that time.
*Death numbers were revised after the recent research from over 140,000 to 105,000 because there were several double countings.
The Great East Japan Earthquake and Tsunami (GEJET) disaster is the deadliest disaster after the Second World War in Japan. The earthquake happened at 2:46 p.m. on March 11th, 2011. The total casualty number is 19,846 based on the EM-DAT. The maximum . tsunami height is 40m on the Sanriku Ria Coast. The first wave arrives approximately 30 minutes after the earthquake.
The Sanriku areas have a special geographical condition mentioned as the Sanriku Ria Coast. The coast has mountains close to the sea, so residential areas are limited only in the narrow and lower zones near the sea, and the areas become very vulnerable against the tsunamis. The bays on the coast are small, and the sea inside the bays is very deep. This makes tsunamis faster and higher, which is why the Sanriku Ria Coast has the highest tsunami risk area in the world.
Because of these characteristics, the communities on the Sanriku Ria coast, mainly in Iwate prefecture, have historically been severely affected by tsunami disasters such as the Meiji Sanriku Tsunami (1896), Sowa Sanriku Tsunami (1933), and Chilean Earthquake Tsunami (1960), compared to the flat coast mainly in Miyagi prefecture and other areas in Japan.
I will explain a little bit about the Meiji (1896). This disaster is so-called a surprise attack. The tsunami disaster happened at approximately . 7:30 p.m. on June 15, 1896, mainly on the Sanriku Ria coast. The dead and missing number has been reported at over 22,000. The earthquake is not so strong (the Japanese earthquake scale indicates Shindo 1-2); however, the tsunami is very strong and high (the maximum height is 38.2m in the Ayasato area (present-day Ofunato city)) compared to the earthquake movement scale. This has severe impacts.We call this huge tsunami caused by a weak earthquake Tsunami Earthquake. The first wave arrives approximately 35 meters after the earthquake. The Meiji (1896) has been the worst tsunami disaster ever in Japan.
In 1611, the larger tsunami (Keicho Sanriku Tsunami*) than Meiji hit the Sanriku area. That could also be a “tsunami earthquake.” After that, every 40 years, the people in the area tended to have a big tsunami. Even though they had such experiences, they did not have good tsunami disaster countermeasures, and the tsunami was a “tsunami earthquake.” In addition, they had some ancient traditions, like the idea that a tsunami was a punishment from the gods and Buddha. These are the main causes that made the Meiji worse.
