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The ) was a powerful
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
6.6 earthquake that occurred 10:13 local time (01:13 UTC) on July 16, 2007, in the northwest
Niigata Prefecture is a Prefectures of Japan, prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,131,009 (1 July 2023) and is the List of Japanese prefectures by area, fifth-largest prefecture of Japan by geographic area ...
of Japan. The earthquake, which occurred at a previously unknown offshore fault shook Niigata and neighbouring prefectures. The city of Kashiwazaki and the villages of Iizuna and Kariwa registered the highest seismic intensity of a strong 6 on Japan's ''shindo'' scale, and the quake was felt as far away as Tokyo. Eleven deaths and at least 1,000 injuries were reported, and 342 buildings were completely destroyed, mostly older wooden structures. Prime Minister
Shinzō Abe Shinzo Abe (21 September 1954 – 8 July 2022) was a Japanese politician who served as Prime Minister of Japan and President of the Liberal Democratic Party ( LDP) from 2006 to 2007 and again from 2012 to 2020. He was the longest-serving pri ...
broke off from his election campaign to visit Kashiwazaki and promised to "make every effort towards rescue and also to restore services such as gas and electricity".


Tectonic summary

This magnitude 6.6 earthquake occurred approximately off the west coast of
Honshū , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the seventh-largest island in the world, and the second-most populous after the Indonesian ...
, Japan, in a zone of compressional deformation that is associated with the boundary between the Amur Plate and the Okhotsk microplate. At this latitude, the Okhotsk Plate is converging to the west-northwest towards the Amur Plate with a velocity of about 9 mm/yr and a maximum convergence rate of 24 mm/yr. The Amur and Okhotsk plates are themselves relatively small plates that lie between the Eurasian plate and the Pacific plate. The Pacific plate converges west-northwest towards the Eurasia plate at over 90 mm/yr. Most of the relative motion between the Pacific and Eurasia plates is accommodated approximately to the east-southeast of the epicenter of the earthquake, where the Pacific plate subducts beneath the Okhotsk Plate. This shallow crustal earthquake was followed 13 hours later by a deep focus magnitude 6.8 quake roughly to the west, below the
Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, it ...
. The two earthquakes were generated by different mechanisms. The first earthquake was caused by deformation within the crust of the Okhotsk Plate and the second quake was likely caused by faulting resulting from internal deformation of the subducted Pacific plate. Given their different mechanisms and physical separation of at least 10 rupture lengths, the second earthquake is not considered an aftershock of the first. Shallow earthquakes cause more damage than intermediate- and deep-focus ones since the energy generated by the shallow events is released closer to the surface and therefore produces stronger shaking than is produced by quakes that are deeper within the Earth. The
peak ground acceleration Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an wikt:accelerogram, accelerogram at a ...
generated was 993 gal (1.01 ''g''). Two days after the initial earthquake, an aftershock, registering shindo 4, occurred in
Izumozaki, Niigata is a Towns of Japan, town located in Niigata Prefecture, Japan. , the town had an estimated population of 4,190, and a population density of 94.4 persons per km2. The total area of the town was . Geography Izumozaki is located in a coastal reg ...
.


Intensity


Automotive production

On July 18,
Toyota is a Japanese Multinational corporation, multinational Automotive industry, automotive manufacturer headquartered in Toyota City, Aichi, Japan. It was founded by Kiichiro Toyoda and incorporated on August 28, 1937. Toyota is the List of manuf ...
motor announced it stopped production in all of its factories because of the damage done to the Riken parts plant in
Kashiwazaki, Niigata is a Cities of Japan, city located in Niigata Prefecture, Japan. , the city had an estimated population of 81,836 in 34,883 households, and a population density of 187 persons per km². The total area of the city was . Geography Kashiwazaki i ...
.
Nissan is a Japanese multinational Automotive industry, automobile manufacturer headquartered in Yokohama, Kanagawa, Japan. The company sells its vehicles under the ''Nissan'' and ''Infiniti'' brands, and formerly the ''Datsun'' brand, with in-house ...
also had to shut down two factories. Production resumed in Toyota,
Mazda is a Japanese Multinational corporation, multinational automotive manufacturer headquartered in Fuchū, Hiroshima (town), Fuchū, Hiroshima Prefecture, Hiroshima, Japan. The company was founded on January 30, 1920, as Toyo Cork Kogyo Co., Ltd. ...
, and
Honda commonly known as just Honda, is a Japanese multinational corporation, multinational Conglomerate (company), conglomerate automotive manufacturer headquartered in Minato, Tokyo, Japan. Founded in October 1946 by Soichiro Honda, Honda has bee ...
plants on July 25, after damaged equipment and gas and water supplies were restored. Toyota's production losses amounted to between 46,000 or possibly 55,000 vehicles. Nissan lost 12,000 vehicles.


Kashiwazaki-Kariwa Nuclear Power Plant incidents

The earthquake caused a leak of radioactive gases from
Kashiwazaki-Kariwa Nuclear Power Plant The is a large, modern (housing the world's first advanced boiling water reactor or ABWR) nuclear power plant on a site.TEPCO Official Press Release (Japanese)First in Japan – Use of the Full Area for Power Plant Buildings, Reinforced Concr ...
. A small amount of water from the spent fuel pool leaked out but plant operators said the leak was insignificant and did not present any environmental danger. The earthquake also caused a fire in an electrical transformer at the plant that was extinguished after two hours. The government requested that the plant remain closed pending safety inspections. The
International Atomic Energy Agency The International Atomic Energy Agency (IAEA) is an intergovernmental organization that seeks to promote the peaceful use of nuclear technology, nuclear energy and to inhibit its use for any military purpose, including nuclear weapons. It was ...
offered to send a team of experts to inspect the plant. The Japanese government initially declined the offer but later accepted it after
Niigata Prefecture is a Prefectures of Japan, prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,131,009 (1 July 2023) and is the List of Japanese prefectures by area, fifth-largest prefecture of Japan by geographic area ...
legislature asked for confidence building efforts to counter public concern about the reactor. Following the incident Dr Kiyoo Mogi, chair of Japan's
Coordinating Committee for Earthquake Prediction The Coordinating Committee for Earthquake Prediction (CCEP) (Japanese language, Japanese: 地震予知連絡会, ''Jishin Yochi Renraku-kai'') in Japan was founded in April 1969,Hamaoka Nuclear Power Plant, which was built close to the centre of the expected Tōkai earthquake.Quake shuts world's largest nuclear plant
''Nature'', vol 448, 392–393, , published July 25, 2007. Retrieved March 18, 2011.
Nuclear crisis in Japan as scientists reveal quake threat to power plants
The Times, published July 19, 2007. Retrieved March 18, 2011.


See also

* List of earthquakes in 2007 * List of earthquakes in Japan


Sources


External links

* {{DEFAULTSORT:2007 Chuetsu Offshore Earthquake Earthquakes of the Heisei era Chuetsu Earthquake, 2007 History of Niigata Prefecture Chuetsu earthquake July 2007 in Japan Niigata Prefecture 2007 disasters in Japan