2007 Chūetsu offshore earthquake

2007 Chūetsu Offshore Earthquake

UTC time	??
Magnitude	6.6 Mw
Areas affected	Japan
Casualties	11 dead, over 1120 injured

The Chūetsu Offshore Earthquake (Template:Lang-ja ) was a powerful magnitude 6.6 earthquake that occurred 10:13 a.m. local time (01:13 UTC) on July 16, 2007, in the northwest Niigata region of Japan. The earthquake 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, but the quake was felt as far away as Tokyo. Eleven deaths and at least 1000 injuries were reported, and 342 buildings were completely destroyed, mostly older wooden structures.

Prime Minister Shinzo Abe broke off from his election campaign in Southern Japan to visit Kashiwazaki and promised to "make every effort towards rescue and also to restore services such as gas and electricity".

Tectonic summary

The landslide of Ōmigawa Station (July 2007)

This magnitude 6.6 earthquake occurred near the west coast of Honshū, Japan, in a zone of compressional deformation that is associated with the boundary between the Amur plate and the Okhotsk plate. At this latitude, the Okhotsk Plate is converging to the west-northwest towards the Amur Plate with a velocity of about 9 mm/yr. The Amur and Okhotsk plate 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 plate and the Eurasia plate is accommodated approximately 400 km 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 330 km to the west, 350 km below the Sea of Japan. 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.

Two days after the initial earthquake, an aftershock occurred, registering 4 shindo in Izumozaki, Niigata

Ceased Auto Production

Toyota motor announced Wednesday that will stop production in all of its factories for the rest of the week because damage done to the Riken parts plant in Kashiwazaki, Niigata. Nissan also had to shut down two factories. The delays may affect delivery schedule, but that is not yet clear.

Production resumed in Toyota, Mazda, and Honda plants on July 25, after damaged equipment and gas and water supplies were restored. It is estimated that Toyota's production losses will amount to 46,000 or possibly 55,000 vehicles, the estimate for Nissan is 12,000, but it is hoped that those cars will be made up by overtime work and faster production.

Kashiwazaki-Kariwa Nuclear Power Plant incidents

A fire broke out in an electrical transformer at the Kashiwazaki-Kariwa Nuclear Power Plant. The fire was extinguished within two hours. The earthquake also caused a leak of radioactive gases. A small amount of water from the spent fuel pool had also leaked, but plant operators are quoted saying the leak was low and did not present any environmental danger.

Damages to the reactors were not severe, but there was much misinformation mainly in non-Japanese media.

• "the plant was cracked"
• "10,000 refugees from nuclear plant accident" (there were 9,000 refugees, from damaged houses or crashed houses. Not related to radioactive material leakage)

The area, ordinarily with a strong tourism industry in the critical summer months, was hard hit by cancellations due to fears relating to the plant.

The government has requested that the plant remain closed pending safety inspections. The IAEA 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 asked for confidence building efforts to counter public concern about the reactor. See also: Effects of the Chūetsu offshore earthquake on the Kashiwazaki-Kariwa Nuclear Power Plant

See also

• 2007 Noto earthquake
• 2004 Chūetsu earthquake
• Great Hanshin earthquake