Seismic reflection imaging of a Warm Core Ring south of Hokkaido
Seismic reflection imaging of a Warm Core Ring south of Hokkaido
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DOI：
10.1071/eg11004
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发表时间：
2011-03
影响因子：
0.9
通讯作者：
M. Yamashita;Kanako Yokota;Y. Fukao;S. Kodaira;S. Miura;K. Katsumata
中科院分区：
文献类型：
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作者：
M. Yamashita;Kanako Yokota;Y. Fukao;S. Kodaira;S. Miura;K. Katsumata
2009年开展了一项多道地震反射(MCS)调查，以探索北海道以南太平洋板块的深部地壳结构。这条勘测线恰好横穿了一个250公里宽的温暖核心环(WCR)，这是由黑潮延伸产生的一个洋流。我们试图利用这些MCS数据来描绘WCR的精细结构。这条测线由两条剖面组成：一条炮距为200米，另一条炮距为50米。炮点线密度较大的记录比炮点线稀疏的记录显示的背景噪声要大得多。我们从之前的拍摄中确定了这种噪音的来源是海面、海底和次海面之间的声学混响。结果表明，在同时测温获得声速信息的情况下，叠前偏移技术可以有效地增强埋藏在背景噪声中的信号。WCR在声学上是一组向内倾斜的凹形反射层，海洋一侧的坡度较陡(~2°)，海岸一侧的坡度较缓(~1°)。在西铁范围内，我们发现了一个30公里宽的透镜状结构，周围有反光板。
A multi-channel seismic reflection (MCS) survey was conducted in 2009 to explore the deep crustal structure of the Pacific Plate south of Hokkaido. The survey line happened to traverse a 250-km-wide Warm Core Ring (WCR), a current eddy that had been generated by the Kuroshio Extension. We attempted to use these MCS data to delineate the WCR fine structure. The survey line consists of two profiles: one with a shot interval of 200 m and the other with a shot interval of 50 m. Records from the denser shot point line show much higher background noise than the records from the sparser shot point line. We identified the origin of this noise as acoustic reverberations between the sea surface, seafloor and subsurface discontinuities, from previous shots. Results showed that a prestack migration technique could enhance the signal buried in this background noise efficiently, if the sound speed information acquired from concurrent temperature measurements is available. The WCR is acoustically an assemblage of concave reflectors dipping inward, with steeper slopes (~2°) on the ocean side and gentler slopes (~1°) on the coastal side. Within the WCR, we recognised a 30-km-wide lens-shaped structure with reflectors on the perimeter.