High-precision estimation of a paleo-tsunami inundation area by identifying tsunami traces beyond sandy tsunami deposits: A case study of the 869 CE Jogan tsunami in Fukushima, northeastern Japan
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引用次数: 0
Abstract
Previous tsunami deposit studies have considered the distribution of visible sandy tsunami deposits as a tool to establish inundation areas and limits, but use of this area for tsunami magnitude estimation may cause it to be underestimated because the actual inundation limit of a tsunami rarely coincide with the depositional limit of visible sandy tsunami deposits. In this study, we aimed to reconstruct with high accuracy the inundation area of the Jogan tsunami, which occurred off the Pacific coast of the Tohoku region of Japan in 869 CE, by using sedimentological and geochemical methods to identify tsunami traces inland from the depositional limit of the tsunami deposits that are difficult to see by eye. We collected sediment samples at Minamisoma City, Fukushima Prefecture. Based on radiocarbon dating, grain-size analysis of sand, increased amounts of marine-derived elements such as Ca and Sr, and the presence of characteristic biomarkers, visible traces of sandy Jogan tsunami deposits were recognized up to 2280 m from the present coastline. Although no visible sandy tsunami deposits were observed farther inland, at 2790 m from the present coastline, evidence of seawater inundation was inferred from computed tomography image analysis, grain-size distribution of sand, presence of pumice, detection of squalene, and other allochthonous biomarkers. Detection of tsunami traces enables a highly accurate estimation of tsunami inundation areas, leading to a more accurate estimation of the source and scale of earthquakes.
期刊介绍:
Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.