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首页> 外文期刊>Journal of oceanography >Sedimentary features of Onagawa Bay, northeastern Japan after the 2011 off the Pacific coast of Tohoku Earthquake: sediment mixing by recolonized benthic animals decreases the preservation potential of tsunami deposits
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Sedimentary features of Onagawa Bay, northeastern Japan after the 2011 off the Pacific coast of Tohoku Earthquake: sediment mixing by recolonized benthic animals decreases the preservation potential of tsunami deposits

机译：2011年东北太平洋地震后日本东北部的Onagawa湾的沉积特征：重新定殖的底栖动物的沉积物混合降低了海啸沉积物的保存潜力

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The huge tsunami waves induced by the 2011 off the Pacific coast of Tohoku Earthquake severely affected shallow marine ecosystems along the Pacific coast of northeastern Japan. This study examined core samples using X-ray radiography, computed tomography scanning, and grain size analysis to identify temporal changes in the physical and biogenic sedimentary structures of seafloor deposits in Onagawa Bay, northeastern Japan, following the 2011 tsunami. Cores were sampled during research cruises in October 2012, December 2013, and April 2014. The seafloor sediments consisted of two lithological layers. The upper section (between the surface and a depth of 8?cm) was composed of muddy sediments deposited by normal depositional processes and/or the weakening tsunami currents. In contrast, the lower part of the cores (below a depth of 8?cm) consisted of tsunami-induced deposits, i.e., horizontally laminated sandy sediments generated by the strong currents associated with the 2011 tsunami. Sampling of these sediments in 2012 and 2013 showed burrows of up to 10?mm in diameter, but restricted to the upper mud layer. In contrast, in 2014, 20–40-mm-diameter mud-filled burrows were seen in both the upper mud and lower sand layers, indicating that recolonization of the seafloor sediment by large and deep-burrowing animals began within 3?years of the 2011 tsunami. The intense sediment mixing by large burrowing animals will homogenize the seafloor sediment and decrease the preservation potential of the tsunami deposits in this bay.
机译：2011年东北地震太平洋沿岸引发的巨大海啸波严重影响了日本东北太平洋沿岸的浅海生态系统。这项研究使用X射线射线照相，计算机断层扫描和粒度分析检查了核心样本，以发现2011年海啸后日本东北部小川湾海底沉积物的物理和生物成因沉积结构的时间变化。在2012年10月，2013年12月和2014年4月的研究航行期间对岩心进行了采样。海底沉积物由两个岩性层组成。上部（在表面和8？cm的深度之间）由通过正常沉积过程和/或减弱的海啸流沉积的泥状沉积物组成。相反，岩心下部（深度小于8？cm）由海啸诱发的沉积物组成，即与2011年海啸相关的强流产生的水平层压的沙质沉积物。在2012年和2013年对这些沉积物进行的采样显示，洞穴的直径最大为10？mm，但仅限于上部泥层。相比之下，2014年，在上层泥层和下层沙层中都看到了直径为20–40 mm的充满泥土的洞穴，这表明大型和深挖动物对海底沉积物进行了重新定殖，开始时间为3年。 2011年海啸。大型穴居动物强烈的沉积物混合将使海底沉积物均匀化，并降低该海湾海啸沉积物的保存潜力。

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