Millennium‐scale recurrent uplift inferred from beach deposits bordering the eastern Nankai Trough,Omaezaki area,central Japan |
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| Authors: | Osamu Fujiwara Kazuomi Hirakawa Toshiaki Irizuki Shiro Hasegawa Yoshitaka Hase Jun‐ichi Uchida Kohei Abe |
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| Institution: | 1. Active Fault and Earthquake Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 7, 1‐1‐1 Higashi, Tsukuba 305‐8567, Japan (email: o.fujiwara@aist.go.jp);2. Graduate School of Environmental Science, Hokkaido University, Kita 10, Nishi 5, Kita‐ku, Sapporo 060‐0810, Japan;3. Department of Geoscience, Interdisciplinary Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue 690‐8504, Japan;4. Graduate School of Science and Technology, Kumamoto University, 2‐39‐1 Kurokami, Kumamoto 860‐8555, Japan;5. Goshoura Cretaceous Museum, 4310‐5 Goshoura, Goshoura‐cho, Amakusa 866‐0313, Japan;6. OYO Corporation, Daitakubo 2‐2‐19, Minami‐ku, Saitama 336‐0015, Japan;7. M T Brain Co. Ltd, 2‐60‐12 Ikebukuro, Toshima‐ku, Tokyo 171‐0014, Japan |
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| Abstract: | A flight of Holocene marine terraces on the southwestern coast of Cape Omaezaki of central Japan provides evidence of recurrent millennium‐scale uplift events. We reconstructed the uplift history of these terraces by using facies analysis of drill core and geoslicer samples, environmental analysis of trace fossils, and 14C age determinations. Coastal uplift can be identified by the displacement of beach deposits such as foreshore deposits, which represent the intertidal swash zone of a wave‐dominated sandy coast. Three levels of former beach deposits facing the Nankai Trough were identified near the coast in the Omaezaki area. The highest of these, dated at about 3020–2880 BC, records a maximum of 2.2–2.7 m of emergence. The middle beach surface, of minimum age 370–190 BC, shows 1.6–2.8 m of emergence. The lowest beach surface, which is older than 1300–1370 AD, records 0.4–1.6 m of emergence. Our analysis of vertical crustal deformation data during the Holocene in this region suggests that rapid and strong uplift was restricted to the southwestern coast of the Omaezaki area and was probably caused by high‐angle thrusting on subsidiary faults branching from the underlying plate boundary megathrust. |
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| Keywords: | beach deposits marine terrace Nankai Trough Omaezaki paleoearthquake uplift |
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