The Chuetsu Earthquakes (中越地震) began at 5:56 p.m. on Saturday, October 23, 2004 (0856 UT, same day). The Japan Meteorological Agency (JMA) has named these the Heisei 16 Niigata Prefecture Chuetsu Earthquakes (平成16年新潟県中越地震) or The Mid Niigata Prefecture Earthquake of 2004.

Damage

The earthquakes have caused extensive damage. As late as November 3, the 39th fatality attributable to the earthquakes occurred as perceptible aftershocks continued. Over 3,000 injuries have been reported in Niigata Prefecture. Over one hundred thousand people fled their homes. The earthquakes caused houses to collapse in Ojiya and damaged thousands in the area.

For the first time in its history, a Shinkansen train derailed while in service. Eight out of ten cars of the Toki 325 (a 200 Series Shinkansen) derailed on the Joetsu Shinkansen line between Nagaoka Station in Nagaoka and Urasa Station in Yamato; no injuries were reported among the 155 passengers. Railbeds, bridges and tunnels were all affected. East Japan Railway Company stopped all trains in Niigata Prefecture, including the extensively damaged Joetsu Line, Shinetsu Main Line , Iiyama Line , Tadami Line and Echigo Line . Part of Nagaoka Station appeared ready to collapse as a result of an aftershock, but after a brief closure, the station has reopened.

The segment of the Joetsu Shinkansen between Echigo Yuzawa Station and Nagaoka Station closed. Buses transferred passengers between the two operating segments of the line: Tokyo Station–Echigo Yuzawa Station and Nagaoka Station–Niigata Station .

On December 27, 2004, service resumed on all remaining parts of the Joetsu and Iiyama Lines reopened. On December 28, 2004, the Joetsu Shinkansen, also reopened, the last to do so.

Japan Highways closed all expressways in Niigata Prefecture. Closures affected the Kanetsu Expressway and the Hokuriku Expressway . As of November 4, the Kanetsu Expressway remained closed between Nagaoka Interchange and Koide Interchange. This segment reopened on November 5.

Landslides and other problems forced closure of two national highways, Route 8 and Route 17, as well as several prefectural roads. This isolated several localities, including nearly the entire village of Yamakoshi in the district of Koshi.

The earthquakes also caused a landslide that partially buried three vehicles. A young boy was rescued from one of these vehicles, but his mother and sister perished. (Recent typhoons had waterlogged the soil, making landslides more likely.)

The quake broke water mains. Extensive electric power, telephone (including cellular telephone) and Internet outages were reported. The cellular telephone system suffered from direct damage to relay stations, as well as depletion of battery back-up power supplies in as little as a day.

Earthquake details

The first quake struck the Chuetsu area of Niigata Prefecture, Japan with a reading of 7 on the Japanese shindo scale at Kawaguchi, Niigata. On the Richter scale, the moment magnitude of the earthquake is estimated at 6.9. (For comparison, the Great Hanshin earthquake, which devastated much of Kobe, measured 7 on the shindo scale, with a magnitude of 7.2.) The earthquake occurred at a depth of 15.8  km. The JMA gave the coordinates of the earthquake as 37.3° N latitude, 138.8° W longitude.

A second earthquake occurred at 6:12 p.m. (16 minutes after the first). This one, at a much shallower depth, also caused a shindo of 6+ and had a magnitude of 5.9. A third, at 6:34, had a shindo of 6−. At 7:46, another shindo 6− earthquake occurred. Intervening and subsequent earthquakes of lesser intensity also shook the region. During the first 66 hours, 15 earthquakes with intensities of shindo 5− or higher rocked the Chuetsu region.

In a press release, the Geographical Survey Institute (GSI) of the Government of Japan published preliminary estimates that a fault having a length of 22 km and a width of 17 km moved approximately 1.4 m.

Background

The shindo scale is a scale of intensity, like the Mercalli Intensity Scale. It provides information related to the severity of shaking at the earth's surface, where it affects structures. In contrast, the magnitude of the earthquake describes the energy released by the quake.

Niigata Prefecture is located in the Hokuriku region of Honshu, the largest island of Japan. The initial earthquake caused noticeable shaking across almost half of Honshu, including parts of the Tohoku, Hokuriku, Chubu, and Kanto regions.

External links

• Geographical Survey Institute site (in English)
• GSI Press Release (in Japanese)
• Japan Meteorological Agency (in English)
• United States Geological Survey on the quake

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