The role of compaction contrasts in sediments in decollement initiation in an accretionary prism
The role of compaction contrasts in sediments in decollement initiation in an accretionary prism
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沉积物压实对比在吸积棱柱中滑脱起始中的作用
DOI：
10.1016/j.margeo.2011.02.011
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发表时间：
2011
期刊：
影响因子：
2.9
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Raimbourg;H.;Ujiie;K.;Kopf;A.;Hisamitsu;T.;Hamano;Y.;Saito;S.;Kinoshita;M.
为了了解沉降是如何发展成原始沉积序列进入俯冲带的，我们对进入日本南海增生棱柱体（ODP站点1173）的沉积柱样品进行了力学测试。在四国下盆地单元上部约100 m厚的区域内，即在地层学上接近棱柱体趾部附近滑脱层实际位置的区域内，施加较大有效压力后，孔隙弹性柔度和塑性收缩均随深度急剧减小。这些属性的对比提供了一个潜在的解释为向外迁移的沉降到传入sediments.When接近变形front. When，一个给定的物质颗粒的影响，增加应力，这有一个组件的垂直加载由于沉积的上覆海沟沉积物，也有一个组件的横向压缩传输的加积楔。根据其初始机械状态，进入的南海沉积柱的横向缩短量随深度而变化，并导致水平速度梯度集中到机械过渡区（位于appx的下四国盆地上段）。450-550米深度），最终沉降传播。未来的工作必须评估这种塑性变形相对于其他控制因素的作用，如摩擦系数和超孔隙压力，无论是在南开和沿着其他活动边缘。
To understand how décollements develop into the pristine sedimentary succession entering subduction zones, we have performed mechanical tests on samples from the sediment column entering the Nankai accretionary prism, Japan (ODP site 1173). Both poroelastic compliance and plastic shrinkage upon application of a large effective pressure sharply decrease with depth in a ~ 100 m-thick domain in the upper section of the Lower Shikoku Basin unit, i.e. in a domain stratigraphically close to the actual location of the décollement near the toe of the prism. These property contrasts provide a potential explanation for the outward migration of the décollement into the incoming sediments.When approaching the deformation front, a given material particle is affected by an increase in stress, which has a component of vertical loading due to the deposition of overburden trench sediment, and also a component of lateral compression transmitted from the accretionary wedge. Depending on its initial mechanical state, the amount of lateral shortening in the incoming Nankai sediment column varies with depth and causes horizontal velocity gradients that concentrate into the mechanical transition zone (upper section of the Lower Shikoku Basin at appx. 450–550 m depth) into which the décollement eventually propagates. Future work has to assess the role of this plastic deformation relative to other governing factors such as friction coefficient and excess pore pressure, both at Nankai and along other active margins.