Earthquake and Tsunami

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2011 Great East Japan Earthquake and tsunami

Introduction

The 2011 Tōhoku earthquake, also known as the Great East Japan Earthquake,[6][7](Japanese: "Eastern Japan Great Earthquake Disaster" was a magnitude 9.0 (Mw) undersea megathrust earthquake off the coast of Japan that occurred on Friday, 11 March 2011 It was the most powerful known earthquake to have hit Japan, and one of the five most powerful earthquakes in the world overall since modern record-keeping began in 1900.  In addition to loss of life and destruction of infrastructure, the tsunami caused a number of nuclear accidents, The Japanese National Police Agency has confirmed 15,538 deaths,[4][5] 5,685 injured,[4][5] and 7,060 people missing. 45,700 buildings were destroyed and 144,300 were damaged by the quake and tsunami.

 

Earthquake

the epicenter was located approximately 70 kilometres (43 mi) east of the Oshika Peninsula of Tōhoku and the hypocenter at an underwater depth of approximately 32 km (20 mi).

The earthquake triggered extremely destructive tsunami waves of up to 40.5 metres (133 ft) in Miyako, Iwate, Tōhoku.[12][13] In some cases traveling up to 10 km (6 mi) inland.[where?][14]

Geology

This earthquake occurred where the Pacific Plate is subducting under the plate beneath northern Honshu. The Pacific plate, which moves at a rate of 8 to 9 cm (3.1 to 3.5 in) per year, dips under Honshu's underlying plate releasing large amounts of energy. This motion pulls the upper plate down until the stress builds up enough to cause a seismic event.

Energy

This earthquake released a surface energy (Me) of 1.9±0.5×1017 joules,[48] dissipated as shaking and tsunamic energy, which is nearly double that of the 9.1-magnitude 2004 Indian Ocean earthquake and tsunami that killed 230,000 people.

Geophysical impacts

The quake moved portions of northeastern Japan by as much as 2.4 m (7.9 ft) closer to North America,[26][27]making portions of Japan's landmass wider than before. The earthquake shifted the Earth's axis by estimates of between 10 cm (4 in) and 25 cm (10 in).[26][27][28] This deviation led to a number of small planetary changes, including the length of a day and the tilt of the Earth.[28] The speed of the Earth's rotation increased, shortening the day by 1.8 microseconds due to the redistribution of Earth's mass.[

Aftershocks

Japan experienced over 900 aftershocks since the earthquake, with about 60 registering over magnitude 6.0 Mw and at least three over 7.0 Mw. A magnitude 7.7 Mw and a 7.9 Mw quake occurred on March 11[66] and the third one struck offshore on 7 April with a disputed magnitude. Its epicenter was underwater, 66 km (41 mi) off the coast of Sendai. The Japan Meteorological Agency assigned a magnitude of 7.4 MJMA,

Tsunami

The earthquake which was caused by 5 to 8 meters upthrust on a 180-km wide seabed at 60 km offshore from the east coast of Tōhoku[74] resulted in a major tsunami which brought destruction along the Pacific coastline of Japan's northern islands and resulted in the loss of thousands of lives and devastated entire towns. The tsunami propagated across the Pacific, and warnings were issued and evacuations carried out. In many countries bordering the Pacific, including the entire Pacific coast of North and South America from Alaska to Chile;[75][76][77] however, while the tsunami was felt in many of these places, it caused only relatively minor effects. Chile's section of Pacific coast is one of the furthest from Japan, at about 17,000 km (11,000 mi) away,[78] but still was struck by tsunami waves 2 m (6.6 ft) high.[79][80] A wave height of 38.9 meters (128 ft) was estimated at Omoe peninsula, Miyako city, Iwate prefecture.

Elsewhere across the Pacific

 Pacific Tsunami Warning Center issued a widespread tsunami warning covering the entire Pacific Ocean.[121][122]Russia evacuated 11,000 residents from coastal areas of the Kuril Islands.[123] The United States West Coast and...
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