Report of field survey for the Niigataken Chuetsu-oki Earthquake in 2007 (Mw = 6.6) [update 18/Jul./2007]
Date: 16-17/Jul./2007
Member: Hiroyuki Goto (DPRI), Kimiyuki Asano (DPRI), Takeshi Morii (Department of Architecture and Architectural Engineering), Masumi Yamada (Pioneering Research Unit for Next Generation), Masayuki Kuriyama (graduate student), Yayoi Ishii (graduate sturent)
1. Introduction
In the morning on 16th, July, 2007, the Niigataken Chuetsu-oki earthquake (Mw 6.6) attacked Hokuriku district, middle northern part of Japan. 10 victims and hondreds of collapsed houses have already reported. We briefly report the field survey at Chuetsu region [red square] just after the earthquake.
Fig.1 Intensity map [□: waveforms are available, △: not available]，aftershock hypocenter distribution for 1 day provided by Hi-net, NIED, and CMT solution provided by F-net, NIED.

2. Kashiwazaki (downtown)
About 15cm steps were observed at the approach of the bridge on R252.
Collupsed houses and the evidence of liquefaction were observed on R252.
Kashiwazaki Site observed 6+ JMA seismic intensity scale and over 100 cm/s peak velocity on NS component. A stone masonry and stone walls were collapsed.
The belfry jumped to the eastern side. The "belfry jumpings" were also observed during the Noto hanto earthquake and the Kobe earthquake.
The elevated walkway was damaged by the buckling at the fixed edge.
3. Kariwa
Many steps on the road, gradient of the electric poles, and the evidence of liquefaction were observed on R8 and R116.
Kariwa site observed 6+ JMA seismic intensity scale. The windows of the office building were broken just over the instrument.
4. Kashiwazaki (Nishiyama town)
Nishiyama site also obserbed 6+ JMA seismic intensity scale. The evidence of liquefaction was recognized in front of the office building.
Cracks over about 300m were observed at the walkway on R116. The walkway was constructed by about 2m height banks.
About 40cm steps were observed at the approach of the bridge on R116.
5. Iizuna
Iizuna site also obserbed 6+ JMA seismic intensity scale, however the site is located over 50km far from the hypocenter. We did not observed stractural damages around the instrument.
6. Acknowledgement
The report used the data provided by K-net, KiK-net, Hi-net and F-net, National Research Institute for Earth Science and Disaster Prevention. We thank many researchers for providing great information: Prof. Sawada (Kyoto Univ.), Prof. Iwata (Kyoto Univ.).
(Written by Hiroyuki Goto)

	Dynamics of Foundation Structure, Disaster Prevention Research Institute, Kyoto University