April 2011 Miyagi earthquake
Encyclopedia
The April 2011 Miyagi earthquake was a magnitude 7.1 Mw
earthquake
, with an epicentre
off the coast of Miyagi Prefecture
, approximately 66 kilometres (41 mi) east of Sendai, Japan. The earthquake was classified as an aftershock
of the March 11 Tōhoku earthquake
, and occurred at 23:32 JST
(14:32 UTC
) on Thursday, 7 April 2011.
Immediately following the tremor, several tsunami warnings were issued for the northeastern coast of Honshu
, but they were all canceled 90 minutes later. Over 3 million households in the area were left without power, and several nuclear plants suffered minor inconveniences. No major damage was reported, though at least 4 people are confirmed dead as a result of the quake, with at least another 141 injured.
7.1 (MW
) earthquake occurred undersea
in the western Pacific Ocean
on 7 April 2011 at 14:21 UTC, approximately 66 km (41 mi) east of Sendai at a depth of 49 km (30.4 mi). The quake was a direct result of thrust–reverse faulting on or near the subduction zone plate boundary
between the Pacific
and North American Plate
s. Initially estimated at a magnitude of 7.4, the tremor was felt in several areas near the east coast of Honshu as an aftershock of the 11 March magnitude 9.0 megathrust Tōhoku earthquake
. The aftershock sequence of this event is ongoing since 11 March, and includes over 58 earthquakes of magnitude 6.0 or greater up until 7 April 2011, with only two others of magnitude 7.0 or greater. Although the quake was located several miles offshore, moderate to very strong shaking was reported as far inland as Tokyo, about 333 km (207 mi) from its epicentre.
issued a tsunami warning for Miyagi Prefecture, as well as tsunami alerts for Iwate Prefecture
, Fukushima Prefecture
, Aomori Prefecture
, Ibaraki Prefecture
and the Pacific Rim
. Waves of between 0.5 to 1 m were anticipated, and residents along coastal areas were urged to evacuate. All warnings and alerts were canceled within 90 minutes, however. The tremor caused widespread power outages, with power still not restored to some 3.6 million households across several prefectures by 8 April. Nuclear power plants within the region also suffered from the outages; two of three power lines servicing as fuel coolers were cut off at the Onagawa power plant
. Radioactive water consequently leaked out of spent fuel pools at three of its reactors, though no change in the radiation levels outside the plant was reported. Five coal-powered power plants also shut down, adding to concerns over energy shortages. Fukushima I power plant
, which had earlier been struck by the 11 March quake, evacuated its workers as a safety precaution, but the plant sustained no damage.
Four people were reported dead as a result of the earthquake, including an elderly woman in Yamagata Prefecture
who lost power to her medical ventilator. An additional 141 people suffered minor injuries, ranging from cuts and bruises to bone fractures. No major losses were reported, though some roads sustained damage, as well as a few homes. The Nikkei index
fell sharply at the closing but rebounded the next day when reports of limited damage were confirmed.
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
, with an epicentre
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
off the coast of Miyagi Prefecture
Miyagi Prefecture
is a prefecture of Japan in the Tōhoku Region on Honshu island. The capital is Sendai.- History :Miyagi Prefecture was formerly part of the province of Mutsu. Mutsu Province, on northern Honshu, was one of the last provinces to be formed as land was taken from the indigenous Emishi, and became the...
, approximately 66 kilometres (41 mi) east of Sendai, Japan. The earthquake was classified as an aftershock
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...
of the March 11 Tōhoku earthquake
2011 Tōhoku earthquake and tsunami
The 2011 earthquake off the Pacific coast of Tohoku, also known as the 2011 Tohoku earthquake, or the Great East Japan Earthquake, was a magnitude 9.0 undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday, 11 March 2011, with the epicenter approximately east...
, and occurred at 23:32 JST
Japan Standard Time
Japan Standard Time or JST is the standard timezone of Japan, and is 9 hours ahead of UTC. For example, when it is midnight in UTC, it is 09:00 in Japan Standard Time. There is no daylight saving time, though its introduction has been debated several times. Japan Standard Time is the same as...
(14:32 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
) on Thursday, 7 April 2011.
Immediately following the tremor, several tsunami warnings were issued for the northeastern coast of Honshu
Honshu
is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...
, but they were all canceled 90 minutes later. Over 3 million households in the area were left without power, and several nuclear plants suffered minor inconveniences. No major damage was reported, though at least 4 people are confirmed dead as a result of the quake, with at least another 141 injured.
Earthquake
The magnitudeMoment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
7.1 (MW
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
) earthquake occurred undersea
Submarine earthquake
A submarine, undersea, or underwater earthquake is an earthquake that occurs underwater at the bottom of a body of water, especially an ocean. They are the leading cause of tsunamis...
in the western Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
on 7 April 2011 at 14:21 UTC, approximately 66 km (41 mi) east of Sendai at a depth of 49 km (30.4 mi). The quake was a direct result of thrust–reverse faulting on or near the subduction zone plate boundary
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
between the Pacific
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
and North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
s. Initially estimated at a magnitude of 7.4, the tremor was felt in several areas near the east coast of Honshu as an aftershock of the 11 March magnitude 9.0 megathrust Tōhoku earthquake
2011 Tōhoku earthquake and tsunami
The 2011 earthquake off the Pacific coast of Tohoku, also known as the 2011 Tohoku earthquake, or the Great East Japan Earthquake, was a magnitude 9.0 undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday, 11 March 2011, with the epicenter approximately east...
. The aftershock sequence of this event is ongoing since 11 March, and includes over 58 earthquakes of magnitude 6.0 or greater up until 7 April 2011, with only two others of magnitude 7.0 or greater. Although the quake was located several miles offshore, moderate to very strong shaking was reported as far inland as Tokyo, about 333 km (207 mi) from its epicentre.
Damage and casualties
Upon the detection of an earthquake, the Japan Meteorological AgencyJapan Meteorological Agency
The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...
issued a tsunami warning for Miyagi Prefecture, as well as tsunami alerts for Iwate Prefecture
Iwate Prefecture
is the second largest prefecture of Japan after Hokkaido. It is located in the Tōhoku region of Honshū island and contains the island's easternmost point. The capital is Morioka. Iwate has the lowest population density of any prefecture outside Hokkaido...
, Fukushima Prefecture
Fukushima Prefecture
is a prefecture of Japan located in the Tōhoku region on the island of Honshu. The capital is the city of Fukushima.-History:Until the Meiji Restoration, the area of Fukushima prefecture was known as Mutsu Province....
, Aomori Prefecture
Aomori Prefecture
is a prefecture of Japan located in the Tōhoku Region. The capital is the city of Aomori.- History :Until the Meiji Restoration, the area of Aomori prefecture was known as Mutsu Province....
, Ibaraki Prefecture
Ibaraki Prefecture
is a prefecture of Japan, located in the Kantō region on the main island of Honshu. The capital is Mito.-History:Ibaraki Prefecture was previously known as Hitachi Province...
and the Pacific Rim
Pacific Rim
The Pacific Rim refers to places around the edge of the Pacific Ocean. The term "Pacific Basin" includes the Pacific Rim and islands in the Pacific Ocean...
. Waves of between 0.5 to 1 m were anticipated, and residents along coastal areas were urged to evacuate. All warnings and alerts were canceled within 90 minutes, however. The tremor caused widespread power outages, with power still not restored to some 3.6 million households across several prefectures by 8 April. Nuclear power plants within the region also suffered from the outages; two of three power lines servicing as fuel coolers were cut off at the Onagawa power plant
Onagawa Nuclear Power Plant
The is a nuclear power plant located on a 1,730,000 m2 site in Onagawa in the Oshika District and Ishinomaki city, Miyagi Prefecture, Japan. It is managed by the Tohoku Electric Power Company...
. Radioactive water consequently leaked out of spent fuel pools at three of its reactors, though no change in the radiation levels outside the plant was reported. Five coal-powered power plants also shut down, adding to concerns over energy shortages. Fukushima I power plant
Fukushima I Nuclear Power Plant
The , also known as Fukushima Dai-ichi , is a disabled nuclear power plant located on a site in the towns of Okuma and Futaba in the Futaba District of Fukushima Prefecture, Japan. First commissioned in 1971, the plant consists of six boiling water reactors...
, which had earlier been struck by the 11 March quake, evacuated its workers as a safety precaution, but the plant sustained no damage.
Four people were reported dead as a result of the earthquake, including an elderly woman in Yamagata Prefecture
Yamagata Prefecture
-Fruit:Yamagata Prefecture is the largest producer of cherries and pears in Japan. A large quantity of other kinds of fruits such as grapes, apples, peaches, melons, persimmons and watermelons are also produced.- Demographics :...
who lost power to her medical ventilator. An additional 141 people suffered minor injuries, ranging from cuts and bruises to bone fractures. No major losses were reported, though some roads sustained damage, as well as a few homes. The Nikkei index
Nikkei 225
The , more commonly called the Nikkei, the Nikkei index, or the Nikkei Stock Average , is a stock market index for the Tokyo Stock Exchange . It has been calculated daily by the Nihon Keizai Shimbun newspaper since 1950. It is a price-weighted average , and the components are reviewed once a year...
fell sharply at the closing but rebounded the next day when reports of limited damage were confirmed.