Earthquakes in Japan
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Earthquakes occur due to the constant movement of the earth’s plate (plate tectonics). Due to sudden movements along the faults that is planar fractures and gradual motion referred to as creep, opposite sides of the plate stretch. This force applied on the plates finally exceeds their strength and they strain. Strain usually occurs along the boundaries of the plate. This results in volcanic eruptions. This motion may also release stress in the form of seismic energy and the plates return to their unrestrained state (elastic rebound theory). Where the first rupture occurs on the plates is referred to as the focus and may be shallow (<100 kilometers) or deep (>300kilometers). A deep focus causes less harm than a shallow focus. The location on the earth’s surface just directly above the focus is referred to as the epicenter CITATION Und14 l 1033 (Understanding Earthquakes, 2014). The Japan archipelago is prone to earthquakes and tsunamis since it sits and/or is near an area where four oceanic and continental plates meet. These plates are the Pacific, North American, Filipino, and the Eurasian plates. These plates are continuously in motion.
Physical Aspects
Japan is an archipelago that consists of 6,852 islands with 75% of its land being mountainous, forested and heavily wooded. The main islands are Honshu, Kyushu, Shikoku, and Hokkaido, with the largest being Honshu and is referred as the mainland. Most of the land in Japan is inhabitable and has therefore been extensively modified by rand reclamation methods, the razing of mountains and hills, and development of artificial islands. Studies have stated, that despite Japan being a very small area, it has been struck by about 10% of the earth’s earthquakes. Japan’s location, on the boundaries of four tectonic plates, makes it susceptible to earthquakes. The earth’s plates move in different directions at a speed of a few centimeters annually. Great forces are applied on the plate boundaries by tectonic motion. Earthquakes may also occur inland due to the accumulated strain on the continental plate.
Figure SEQ Figure * ARABIC 1 Pacific Plate Boundary, where majority of earthquakes and eruptions occur
Japan has experienced some large earthquakes on its continental plate that have resulted in the fault displacement reaching the ground surface and deforming the geological layers and geographical features. These deformations caused by repetitive fault movements eventually form characteristic geographies. The dislocations include continuous cliff formations, dislocations on valleys, and dislocations on mountain ridges. Today, geologists estimate that Japan has more than 2, 000 active faults. This region is therefore referred to as the “Pacific Ring of Fire”.
Areas with these active faults and large-scale subduction have been identified to be prone to earthquakes. Large-scale earthquakes usually occur repeatedly at the same place. For instance, the Nankai Trough, an area where subduction earthquakes occur, has been identified to experience large-scale earthquakes repeatedly. Studies have also shown that large-scale inland earthquakes occur repeatedly.
Japan is also very likely to suffer tsunamis due its location in the Pacific Ocean. If an earthquake results in a large crustal deformation under the ocean, it moves the overlying mass of water, and causes a tsunami. Tsunamis therefore occur due to large earthquakes occurring in the ocean. After an earthquake occurs, a tremendous crustal deformation results in the ocean bed. This causes the overlying seawater to rise and fall. The fluctuation of the water results in a tsunami. However, tsunamis are not only created by earthquakes but volcanic eruptions on the seabed, seabed landslides, or collapses close to the shore. Tsunamis characteristically reduce their velocity and increase in height as they head towards land. The velocity although slowed down is about 40km/h and the water height at 10 meters. The velocity and height are correlated and depend on the magnitude of an earthquake, the shape of the coastline, and the topography of the seafloor.
When an earthquake occurs, part of its energy travels in waves referred to as seismic waves. When the underground rock is broken and a fault shifts, part of the seismic energy is propagated in every direction. Seismic waves contain P (primary) waves and S (secondary) Waves. P waves travel faster than S waves, are the propagation of density change, and the direction of their shake is perpendicular to the direction of their propagation. S wave shake perpendicular to the direction of propagation and are the propagation of shear deformation. P waves are also referred to as longitudinal while S waves are referred to as transverse waves. P waves always occur before the S waves as they are faster and are therefore felt first. They rattle the ground while the S waves sway the ground.
Social, economic, and political aspects
Nearly everyone in Japan is at risk of two or more hazards. These hazards include; floods, earthquakes, landslides, tsunamis, or ground liquefaction. Japan is therefore a multiple hazard zone (MHZ). An MHZ exposes people to greater risks than in other places. According to Degg’s model, there are differences between hazards, vulnerability, and risks, although they are all interrelated. If a vulnerable population is exposed to a hazard where natural and human systems overlap, then a disaster occurs. The larger the magnitude or scale of an earth’s event or process, and the more vulnerable the people, then the larger the magnitude of the natural disaster or hazard.
Economic aspect of development
According to data by the land ministry in Japan, about 58.9 million people are at risk of being hit by an earthquakes CITATION The111 l 1033 (The 2011 off the Pacific coast of Tohoku Earthquake Disaster (92nd Report), 2011). This is approximately 46.3% of the nation’s total population. The economic, social, and political aspects of Japan make it better at handling earthquake disasters more than other nations. Japan’s Human Development Index (HDI), for instance, is at 0.91. The high HDI is not only linked to economic status, but to health, education, and longevity. Since hazards and disasters are known to make poverty worse, and vice versa, Japan is at a safe place since it does well on a global scale. Japan has the third largest economy globally, and has equitable distribution of wealth and resources, people in Japan have high standards of living, and most of the population is insured. Therefore, Japan is able to handle hazards efficiently. It has systems and structures for mitigating the effects of hazards that are financially backed. Moreover, Japan is able to warn its citizens before the natural hazard strikes.
Social aspect
Japan had high- quality, secure housing built with earthquakes and other hazards in mind, it has enforced the earthquake-resistant housing codes, and it has a high expectancy and an extremely low infant mortality rates. However, when analyzing Japan’s population pyramid, one realizes that it has a large ageing population. This increases its vulnerability since people aged over 65 years are highly unlikely to be agile during a disaster. They also die due to the impact of shock, and other impacts on their chronic illnesses. It is therefore able to manage disasters better. Its Gross Domestic Product (GDP) is estimated to be at $34,200 GDP/cap CITATION Bir12 l 1033 (Birmingham & McNeill, 2012). In terms of preparedness, that is, education and infrastructure, Japan has an average of 11.9 years of schooling, and 75% of the buildings are built with earthquakes in mind.
Environmental aspects
Japan is a world leader in environmental protection. It is involved in massive land reclamation and reforestation policies.
Political aspects
Japan is characterized by an effective government, and by robust systems that have the capacity to deliver during disasters.
History and Perceptions of Hazards
The March 11, 2011 Tohuku Earthquake that occurred off the Pacific Ocean from Tohuku to the Kanto Region was the earthquake Japan has ever experienced. The earthquake had a magnitude of 9.0 and its epicenter was off the coast of Sanriku. The Japan Meteorological Agency (JMA) termed it as the strongest earthquake ever received in the country since Japan began taking magnitude measurements CITATION Pre11 l 1033 (Preliminary Report on Earthquake and Tsunami Disasters, the 2011 off the Pacific coast of Tohoku Earthquake, 2011). The JMA named it, ‘The 2011 off the Pacific Coast of Tohoku Earthquake.’ Data from Japan’s National Police Agency revealed that on September 11, six months after earthquake, and a total of 15,782 people had died (including deaths caused by the tsunami and aftershocks) and 4086 persons were missing. Sixty percent of the persons that had lost their lives were aged sixty-five and above. The number of buildings that had been completely destroyed were 128,530, while those that had been half destroyed totaled to 240,332 CITATION The11 l 1033 (The 2011 off the Pacific coast of Tohoku Earthquake Damage Status and Measures by the Police, Public Information Document , 2011). Buildings on the coast were washed away by the tsunami while those that were inland were destroyed by the seismic waves.
The Cabinet Office of Japan has not provided the overall costs of the damage. However, there have been estimates by these office on the estimated costs CITATION Est11 l 1033 (Estimate of the Cost of Damage in the 2011 off the Pacific coast of Tohoku Earthquake Disaster, 2011). For instance, the buildings were about ¥10.4 trillion, lifeline facilities such as gas, electricity, water supplies, communication, and broadcasting damages cost about ¥1.3 trillion, and infrastructure facilities such as rivers, ports, sewage lines, airports, and roads cost about ¥2.2 trillion. In the end, the earthquake was thought to have costed Japan about ¥ 16-25 trillion.
Japan was not so vulnerable to this disaster since it is a high-income nations and they respond to disasters better using an adaption approach rather than a fatalistic one. Before the earthquake, Japan’s national territory had covered the early warning symptoms. Six months prior to the disaster, 670,000 persons participated in the national earthquake drill that better equipped the citizenry on how to react. Japanese recovered by the government’s quick response to the emergency CITATION Mot12 l 1033 (Kazama & Noda, 2012). The government organized a large emergency respond team, the Ministry of Defense gathered the Self- Defense Forces to assist in the crisis. The National Police and the Fire and Disaster Management Agency to help out in the rescue missions. Regarding awareness, perception, and approach, Japan’s citizenry is aware of these hazards since they regularly occur in the nation CITATION Suz14 l 1033 (Suzuki & Kaneko, 2014). They have therefore adapted to these happenings as their resources allow. Japan’s citizenry tends to be more aware of all the risks affecting them, accepting these risks, and using their ample resources to mitigate the effects of these disasters.
References
BIBLIOGRAPHY Birmingham, L., & McNeill, D. (2012). Strong in the Rain: Surviving Japan’s Earthquake, Tsunami and Fukushima Nuclear Disaster,. Basingstoke: Palgrave Macmillan Trade.
Estimate of the Cost of Damage in the 2011 off the Pacific coast of Tohoku Earthquake Disaster. (2011, June 24). Retrieved from Cabinet Office: 〈http://www.bousai.go.jp〉
Kazama, M., & Noda, T. (2012). Damage statistics (Summary of the 2011 off the Pacific Coast of Tohoku Earthquake damage). Soils and Foundations, 780-792.
Preliminary Report on Earthquake and Tsunami Disasters, the 2011 off the Pacific coast of Tohoku Earthquake. (2011). Retrieved from Japan Meteorological Agency: 〈http://www.jma.go.jp/jma//kishou/books/saigaiji/saigaiji_201101/saigaiji_201101.pdf〉
Suzuki, I., & Kaneko, Y. (2014). Japan’s Disaster Governance: How was the 3.11 Crisis Managed? New York: Springer.
The 2011 off the Pacific coast of Tohoku Earthquake Damage Status and Measures by the Police, Public Information Document . (2011). Retrieved from National Police Agency: 〈http://www.npa.go.jp/archive/keibi/biki/higaijokyo.pdf〉
The 2011 off the Pacific coast of Tohoku Earthquake Disaster (92nd Report). (2011, September 26). Retrieved from Ministry of Land, Infrastructure, Transport and Tourism, 2011a: 〈http://www.mlit.go.jp/saigai/saigai_110311.html〉
Understanding Earthquakes. (2014). Retrieved from The Headquarters for Earthquake Research Promotion: https://www.jishin.go.jp/main/pamphlet/brochures2014en/understanding_earthquakes.pdf
