Japanese Earthquake & Tsunami
2011 Tohoku Earthquake & Tsunami- Japan
What happened - The 2011 Tohoku earthquake was a magnitude 9.0 undersea earthquake off the coast of Japan that occurred on Friday, March 11, 2011. It is also known as the Great East Japan Earthquake. The epicenter was 70 kilometers (43 mi) east of Tohoku on the Oshika Peninsula. It was the most powerful earthquake ever recorded to hit Japan and the fifth most powerful earthquake in the world since modern record-keeping began in 1900. The earthquake triggered powerful tsunami waves whose heights reached over 40 meters (133 ft.) in Miyako near Tōhoku and traveled more than 10 km (6 mi) inland. The earthquake moved Honshu (the main island of Japan) 2.4 m (8 ft) east and shifted the Earth on its axis by estimates of between 10 cm (4 in) and 25 cm (10 in).
The devastation and loss of life in Japan was extraordinary. A Japanese Police Agency report confirmed 15,889 deaths, 6,152 injured, and 2,601 people still missing. This loss of life was aggravated by over 127,000 buildings that collapsed, with a further 272,788 buildings 'half collapsed', and another 747,989 buildings partially damaged. There was also heavy damage to roads and railways as well as fires in many areas, and a dam collapse. Over 4.4 million households in northeastern Japan were left without electricity and 1.5 million without water. There was also critical damage to a nuclear power plant in the area and radiation leakage from that plant.
The Science of Earthquakes & Tsunamis -
Most earthquakes, including the Tohoku, occur along the edges of the tectonic plates that separate continents and oceans from each other. These tectonic plates are formed from the molten magma that rises from the earth's core and then cools and hardens near the surface of the earth. The tectonic plates move slowly toward one another and when they come in contact there is
either a sudden slipping and lifting or one plate 'subducts' (sinks under) the other. Japan is located on the eastern edge of the Eurasian Plate and the North American Plate. The Pacific Plate, which is an oceanic plate, subducts (sinks under) the other two which are called continental plates. Over time, great pressure builds up along the plate edges and is eventually released as an earthquake.
If the earthquake occurs underneath or near the ocean, the sudden release of great energy causes a great shockwave in the water and a tsunami or tidal wave can be formed. The tsunami wave, when formed, may not be very tall where the ocean is deep. But when it reaches the shallow water near land, the friction on the bottom of the wave forces the moving water to rise up. However, even a 5 or 6 foot tsunami wave has so much water moving behind it that it can flood entire coastal areas and cities for miles inland. Because the wave may not be visible from the deeper ocean, many earthquake-caused tsunamis reach land without much warning and thousands of people can be killed or swept away in just a few minutes.
What can be done to prevent future disasters - Although earthquakes and tsunamis are naturally occurring events and cannot be prevented, cities, counties and countries can put in place disaster preparedness plans to lessen the impact of these natural disasters. Many earthquake related deaths and most property damage is related to poor or outdated building practices. People living in areas where earthquakes occur should begin rebuilding and retrofitting their homes, buildings, bridges and dams with more modern, earthquake-resistant construction, though this can be very expensive, especially for poorer nations. This has been done all over the San Francisco Bay Area after the 1989 Loma Prieta quake, including building a new span of the Oakland-Bay Bridge. To lessen tsunami deaths and damage, cities and countries near the ocean can also invest in raising sea walls, building earthen berms and drainage ditches near the beaches and even moving vulnerable housing, hospitals and emergency services away from the oceanfront or to upper levels of beachfront buildings. Developing early warning systems to predict, recognize and alert citizens about approaching tsunami waves is critical in helping get people to move to higher ground before the wave hits land. Although no systems or building practices can completely prevent destruction from earthquakes and tsunamis, planning ahead and spending money before the disaster occurs can save many lives and reduce the cost of property damage.
Who can help in a natural disaster? In the event of a natural disaster, emergency services such as fire departments, police departments and emergency medical services are often the first to respond. Schools and hospitals are also places of refuge for local citizens and teaching and hospital staff are expected to remain at their places of work to help out. Local governments can call on the state's National Guard to help with rescue efforts and to prevent rioting or looting. In the event of a large disaster (think Hurricane Katrina and Tohoku) national governments can call on the Coast Guard and armed services personnel if the impact is too large for local and state agencies. Also, many non-profit, social service agencies are entrusted with disaster-preparedness plans to help feed, clothe and shelter their neighborhoods' citizens in the event of a natural disaster.
– Created by Scott Fletcher, Library Director
Tsunami Video – National Geographic