Sedimentary processes and spatial distributions of tsunami deposits in valleys have poorly been understood despite many paleo-tsunami deposits have recently been discovered from sedimentary sequences in valleys. We conducted an exhaustive investigation of 2011 Tohoku-oki tsunami deposits in a narrow valley at the south end of Sendai Plain, northeastern Japan, to collect sedimentological data of the tsunami deposits in the valley and to correlate them with tsunami inundation and associated sedimentary processes. The tsunami deposits were investigated at 174 sites to cover the entire inundation area of the narrow valley. We analyzed thickness, sedimentary structures, and grain size of the tsunami deposits to correlate their spatial variation with tsunami flow hydrodynamics and topographic features. The tsunami deposits, composed of sand and mud layers, were found to be 0–40 cm thick. Sand thickness generally decreased inland with local fluctuation. The sand layer was mostly composed of single unit on the upper main valley and sub-valleys, although it was mainly composed of 2–6 sub-units on the lower main valley and in the pond. Mud thickness is strongly controlled by local sources, namely, the rice paddy and the pond. The depositional area of the mud layer coincides with the distribution of the rice paddies and the pond location. The mud layer also considerably thicker in and around the pond. These results indicate that sediment thickness and sedimentary structures are highly varied on a local scale, but they are generally controlled by local topography. Sediment budget in the valley was estimated, and it may provide implications to general sedimentary process. Total depositional volume of the tsunami sand deposited on land is half of the volume of sediments disappeared from the sandy beach and sand dune, suggesting the rest must have been discharged into the sea by the backwash. Spatial distribution of sediment thickness and sedimentary structures as well as sedimentary processes inferred from 2011 Tohoku-oki tsunami deposits will benefit searching and identification of paleo-tsunami deposits in valleys of other coastal environments.

中文翻译：

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狭窄山谷环境中海啸沉积物的空间分布和来源-2011年日本东北部东北冲海海啸沉积物的见解

尽管最近从山谷的沉积序列中发现了许多古海啸沉积物，但人们对山谷海啸沉积物的沉积过程和空间分布知之甚少。我们对日本东北部仙台平原南端狭窄山谷中的2011年东北冲海啸海床进行了详尽的调查，以收集该谷海啸海床的沉积学数据，并将其与海啸淹没及相关的沉积过程联系起来。在174个地点调查了海啸沉积物，以覆盖狭窄山谷的整个淹没区域。我们分析了海啸沉积物的厚度，沉积结构和粒径，以将其空间变化与海啸流动的水动力和地形特征相关联。海啸沉积物，由沙子和泥土层组成的厚度为0-40厘米。随着局部波动，内陆的砂层厚度通常会减小。沙层主要由上部主谷和子谷上的单个单元组成，尽管它主要由下部主谷和池塘上的2-6个子单元组成。泥浆的厚度受稻田和池塘等地方资源的强烈控制。泥层的沉积面积与稻田的分布和池塘的位置相吻合。池塘及其周围的泥浆层也相当厚。这些结果表明，沉积物的厚度和沉积结构在局部范围内变化很大，但是它们通常受局部地形控制。估计了该山谷的泥沙淤积，这可能对总体沉积过程有影响。沉积在陆地上的海啸沙的总沉积量是从沙滩和沙丘中消失的沉积物量的一半，这表明其余部分一定是通过反冲洗而排入海中的。从2011年东北冲木海啸沉积物中推断出的沉积物厚度和沉积结构的空间分布以及沉积过程，将有助于在其他沿海环境的山谷中搜寻和识别古海啸沉积物。