Vein structures, like ripple marks, are formed by short-wavelength shear waves
Vein structures, like ripple marks, are formed by short-wavelength shear waves
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静脉结构，如波纹痕迹，是由短波长剪切波形成的
DOI：
10.1016/j.jsg.2008.02.002
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发表时间：
2008
影响因子：
3.1
通讯作者：
Y. Ogawa
中科院分区：
文献类型：
--
作者：
T. Ohsumi;Y. Ogawa
脉状结构是深海半远洋粘土质和硅质泥岩中汇聚板块边界处的一种独特结构，由紧密排列的充满泥浆的脉状结构组成，形成通常平行于层理面的阵列。该结构被认为是地震过程中由于裂缝共振而形成的震积岩。我们详细的现场观察和振动模型实验证实，无论是基本（第一阶段）还是高级（发达阶段）的静脉结构都可以用系统的理论来解释。本质上，静脉结构是由于剪切而在一系列裂缝中形成的，不是通过推波而是通过非常短波长的剪切波，通过与形成波纹标记的机制非常相似的机制。我们发现静脉阵列的高度 (H) 与静脉间距 (S) 系统相关，使得 H=5S，这表明沉积物的剪切强度与沉积物层驻波部分的厚度成正比。沉积物层的顶部发生剪切流或振荡流，在该流下，波长为毫米至厘米数量级的驻波导致脉状结构的形成。脉状结构不仅可以响应地震震动而形成，还可以通过沿着大断层的剪切波传播或通过与密度或泥石流、滑坡或断层有关的其他类型的剪切而形成。
Vein structure, a distinctive structure in deep-sea hemipelagic clayey and siliceous mudstones at convergent plate boundaries, consists of closely spaced mud-filled veins forming an array usually parallel to the bedding plane. This structure has been regarded as a seismite that formed during earthquake shaking by resonance of fractures. Our detailed field observations and shaking model experiments verified that both basic (first-stage) and advanced (developed-stage) vein structures can be explained by a systematic theory. Essentially, a vein structure forms in an array of fractures as a result of shearing, not by push waves but by shear waves of very short wavelength, by a mechanism very similar to that which forms ripple marks. We found the height of a vein array (H) to be systematically related to vein spacing (S) such that H=5S, suggesting that the shear strength of the sediment is proportional to the thickness of the standing wave part of a sediment layer. Shear or oscillatory flow occurs in the top part of a sediment layer, under which standing waves with wavelengths on the order of millimeters to centimeters lead to vein structure formation. Vein structure can develop not only in response to earthquake shaking but also by propagation of shear waves along a large fault or by other kinds of shears associated with density or debris flows, landsliding, or faulting.