Variation of physical properties beneath a fault observed by a two‐ship seismic survey off southwest Japan
Variation of physical properties beneath a fault observed by a two‐ship seismic survey off southwest Japan
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日本西南部海域双船地震勘测观测到的断层下物理性质的变化
DOI：
10.1029/2004jb003036
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发表时间：
2005
影响因子：
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通讯作者：
J. Kasahara
中科院分区：
文献类型：
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作者：
T. Tsuru;S. Miura;Jin;A. Ito;G. Fujie;Y. Kaneda;T. No;T. Katayama;J. Kasahara
[1] 2002年，我们在日本西南弧附近的熊野滩进行了两船地震反射调查，以澄清从南海海槽俯冲带板块边界分支的张开断层沿线的物理性质。在勘测期间，通过多次通过发射船和接收船，每次通过时间隔不同的恒定偏移量，收集了最大偏移量为 20 公里的地震反射数据。我们对反射极性和振幅随偏移量变化 (AVO) 效应进行了分析，以检查张开断层正下方各层的物理特性。来自张开断层的反射显示出沿着断层的不同极性。在本研究中，我们假设断层上方地层的泊松比为0.30~0.40。当极性反转时，断层正下方层的泊松比估计为 0.33–0.445（平均增加 11%）。在极性正常的情况下，该比率估计为 0.263–0.365（平均下降 11%）。如果正如许多作者所认为的那样，反向极性表明流体的存在，那么极性分析表明流体在张开断层剪切带中的分布不均匀。 AVO分析结果也支持了在某些假设下流体分布空间变化的可能性，因为泊松比随着岩石中流体含量的变化而变化。反射极性的变化和相应的AVO效应可能预示着张开断层剪切带局部流体运移的可能性。
[1] We conducted a two-ship seismic reflection survey at Kumano-nada off the southwest Japan arc, in 2002, in order to clarify physical properties along a splay fault that branches from the plate boundary of the Nankai Trough subduction zone. During the survey, seismic reflection data were collected out to maximum offset of 20 km using multiple passes of a shooting and a receiving vessel separated by a different constant offset on each pass. We conducted analyses on reflection polarity and amplitude variation with offset (AVO) effects to examine physical properties of layers immediately beneath the splay fault. Reflections from the splay fault showed varying polarities along the fault. In the present study, we assumed that the Poisson's ratio of the layer above the fault was 0.30–0.40. Where polarity is reversed, the Poisson's ratio of the layer immediately below the fault was estimated to be 0.33–0.445 (11% increase on average). Where polarity was normal, the ratio was estimated to be 0.263–0.365 (11% decrease on average). If the reverse polarity indicates the existence of fluid as many authors suggest, the polarity analysis demonstrates inhomogeneous distribution of fluid in the splay fault shear zone. The results of AVO analysis also support the possibility of the spatial variation of fluid distribution under some assumptions because the Poisson's ratio changes with content of fluid in rocks. The variation in reflection polarity and corresponding AVO effects may signify the possibility of localized fluid migration in the splay fault shear zone.
影响因子：
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作者：
N. Takahashi;S. Kodaira;A. Nakanishi;Jin-Oh Park;S. Miura;T. Tsuru;Y. Kaneda;K. Suyehiro;H. Kinoshita;N. Hirata;T. Iwasaki
通讯作者：
N. Takahashi;S. Kodaira;A. Nakanishi;Jin-Oh Park;S. Miura;T. Tsuru;Y. Kaneda;K. Suyehiro;H. Kinoshita;N. Hirata;T. Iwasaki
影响因子：
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作者：
A. Nakanishi;N. Takahashi;Jin-Oh Park;S. Miura;S. Kodaira;Y. Kaneda;N. Hirata;T. Iwasaki;Masao Nakamura
通讯作者：
A. Nakanishi;N. Takahashi;Jin-Oh Park;S. Miura;S. Kodaira;Y. Kaneda;N. Hirata;T. Iwasaki;Masao Nakamura
影响因子：
3
作者：
Kikuchi, M;Nakamura, M;Yoshikawa, K
通讯作者：
Yoshikawa, K