Estimation of local site effects in Ojiya city using aftershock records of the 2004 Mid Niigata Prefecture earthquake and microtremors
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- Yamanaka Hiroaki
- Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology
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- Motoki Kentaro
- Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology
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- Fukumoto Shun'ichi
- Tokyo Soil Research
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- Takahashi Toshiyuki
- Tokyo Soil Research
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- Yamada Nobuyuki
- Disaster Prevention Research Institute, Kyoto University
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- Asano Kimiyuki
- Disaster Prevention Research Institute, Kyoto University
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Aftershock observations of the 2004 Mid Niigata Prefecture earthquake were conducted in the central part of Ojiya city, the Niigata prefecture, central Japan, to investigate local site effects. We installed eight accelerographs in the vicinity of the K-NET and JMA stations in the area. The stations of the aftershock observations are situated under different geological conditions including one installed in a mountainous area on Tertiary layers to serve as a reference site. We examined the ground-motion characteristics of the records for a Mj 6.1 aftershock focusing on local site effects. The amplification, at a period of less than 1 sec, is the largest in the vicinity of the K-NET station. The amplification at periods longer than 2 sec is larger in the western part of the city than those in the east. We estimated the S-wave velocity structure in the sediments above the basement with an S-wave velocity of 3.4 km/sec from the inversion of phase velocities measured by the array observations of vertical microtremors. We discuss the amplification factors using the S-wave velocity profile and show that shallow soils over the layer with an S-wave velocity of 0.49 km/sec are responsible for the amplification at periods shorter than 0.4 sec. Deeper sedimentary layers are needed to explain amplification at periods of 1 sec.
収録刊行物
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- Earth, Planets and Space
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Earth, Planets and Space 57 (6), 539-544, 2005
地球電磁気・地球惑星圏学会 、公益社団法人 日本地震学会、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会
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詳細情報 詳細情報について
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- CRID
- 1390282681488749952
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- NII論文ID
- 10017469222
- 130003956523
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- NII書誌ID
- AA11211921
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- ISSN
- 18805981
- 13438832
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- NDL書誌ID
- 7344472
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
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