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Niigata Ken Chuetsu, Japan Clearinghouse  
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Niigata Ken Chuetsu, Japan Earthquake
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Moment Magnitude Mw 6.6
Oct 23, 2004

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This figure was made by Japan Meteorological Agency (JMA)


Moment Magnitude 6.6
Date October 23, 2004
Time 08:56:00 UTC
Epicenter 37.199N, 138.812E
Fault Source
Faulting Mechanism
Affected Cities Niigata, Honshu
Population of Region
Casualties 23 (estimated)
Injuries 1,232 (estimated)
Economic Cost
Last Major Earthquake

For information on the earthquake by USGS, click here.

(summary information provided by various news sources and Charles Scawthorn, professor, Department of Urban Management, Kyoto University, and EERI Reconnaissance Team Leader)
  • Fault length approx. 30 km, 15 km depth of displacement, 1.2 vertical displacement.
  • Strong Motion recorded 1g or greater in at least several locations.
  • Epicenter and most damage seems to be in relatively rural hilly/mountainous areas.
  • Little urban damage.
  • Most damage seems to be landslide and ground failure related.
  • Some wood building collapses.
  • One road tunnel appears to have had a lining breach and inflow of soil.
  • According to the Japanese Meteorological Agency, this is the first time on record in Japan that 4 earthquakes measuring 6 on the Japanese seismic intensity scale occurred in one day.
  • The sudden vertical and horizontal shocks caused houses to collapse, roads to cave in and a Shinkansen bullet train to derail for the first time in its history.
  • One investigator who is back from the field reports damage to a retrofitted Shinkansen structure. The area was within 5 km of the fault, and the nearest instrument (abt 5 km distant) registered130 kine.
  • About 61,000 persons were evacuated throughout the prefecture. Many people spent at least the first night outside.
  • Aftershocks prompted the evacuation of more people, increasing the total number of evacuees who are in schools and other public buildings to about 97,800, with those who want more privacy sleeping in their cars. About 60,000 houses were still out of power.
  • The government immediately set up a task force and sent an 11-member advance team to Niigata Prefecture to precede a visit by disaster management minister Yoshitaka Murata.

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