Subsidence along the central to southern Sanriku coast, northeast Japan, near the source region of the 2011 Tohoku-oki earthquake, estimated from the Holocene sedimentary succession along a ria coast
Subsidence along the central to southern Sanriku coast, northeast Japan, near the source region of the 2011 Tohoku-oki earthquake, estimated from the Holocene sedimentary succession along a ria coast
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DOI：
10.1016/j.quaint.2017.08.008
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发表时间：
2017-10
影响因子：
2.2
通讯作者：
Y. Niwa;T. Sugai;Y. Matsushima;S. Toda
中科院分区：
文献类型：
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作者：
Y. Niwa;T. Sugai;Y. Matsushima;S. Toda
据报道，在日本东北部的三陆海岸，地壳运动存在 105 年规模的隆起与 101-102 年规模的沉降之间的差异。年代明确的全新世切谷充填沉积物提供了千年尺度的垂直地壳运动记录，这是了解该地区构造历史的关键。先前对下切山谷中全新世早期潮间带沉积物的年龄和分布的研究报告称，三陆南部海岸在全新世期间以平均每年约 1 毫米的速度下沉。在这里，我们研究了从三陆海岸中部的津轻石平原收集的三个沉积岩芯：TGI1、TGI2 和 TGI3，并在所有三个岩芯中识别出全新世三角洲沉积序列。在TGI3岩心中，距离最远的内陆地点，潮间带沉积相（7500至7000cal BP沉积）和上覆6米厚的洪泛区相（7000至5000cal BP沉积）均低于当前海平面。由于日本周围的水等静压抬升导致海平面上升于全新世中期，我们推断津轻石平原在全新世期间下沉，估计的下沉速率最大为 1.1–1.9 毫米/年，与最近报道的三陆南部海岸的下沉速率一致。这项研究的结果证实，三陆海岸中部至南部正在下沉，与基于海洋阶地研究的解释相反，该部分海岸正在隆起。这里提供的经验数据将有助于构建与板块俯冲相关的地震周期模型。
Along the Sanriku coast, northeast Japan, discrepancies in crustal movement have been reported between uplift on a scale of 105years versus subsidence on a scale of 101–102years. Well-dated Holocene incised-valley-fill sediments provide records of millennial-scale vertical crustal movement, which is key to understanding the tectonic history in this area. Previous studies of the age and distribution of early Holocene intertidal deposits in incised valleys reported that the southern Sanriku coast has subsided during the Holocene at an average rate of about 1 mm/yr. Here we studied three sediment cores, TGI1, TGI2, and TGI3, collected from the Tsugaruishi plain on the central Sanriku coast, and recognized a Holocene deltaic sediment succession in all three cores. In core TGI3, from the farthest inland site, the intertidal sediment facies, deposited from 7500 to 7000 cal BP, and the overlying 6-m-thick floodplain facies, deposited from 7000 to 5000 cal BP, are both below the present sea level. Because a sea-level highstand due to hydroisostatic uplift around Japan occurred in the mid-Holocene, we inferred that the Tsugaruishi plain subsided during the Holocene, and the estimated subsidence rate, 1.1–1.9 mm/yr at maximum, is consistent with the recently reported subsidence rate along the southern Sanriku coast. The results of this study confirm that the central to southern Sanriku coast is subsiding, in contrast to an interpretation based on the study of marine terraces that this part of the coast is uplifting. The empirical data presented here will be useful for constructing an earthquake cycle model related to plate subduction.