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1 1498 灘 * Geological Survey of Belgium Vanessa HEYVAERT Geomorphic impact by the1498 Meio earthquake along the Hamana River on the Enshu-nada coast, Central Japan: Evidence from the cored sediments Osamu FUJIWARA Active Fault and Earthquake Research Center, AIST, Site C7, Higashi, Tsukuba, Ibaraki, Japan Eisuke ONO Faculty of Education, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, , Japan Toshifumi YATA Faculty of Humanities, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, , Japan Masatomo UMITSU, Yoshiki SATO ** Graduate School of Environmental Studies, Nagoya University, D2-1, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan Vanessa HEYVAERT Geological Survey of Belgium, Royal Belgian Institute for Natural Sciences, Jennerstraat 13, 1000 Brussels, Belgium The AD 1498 Meio earthquake (M8.2~8.4) that occurred along the Nankai Trough and the tsunami generated by the earthquake affected a large impact not only on the coastal geomorphic evolution but also the geographical and social conditions of the port town along the Pacific cost of the central Japan. Excavation survey using the geoslicer and boring machine in the trace of the Hamana River, southern Shizuoka Prefecture, revealed that the river mouth was abruptly closed and a rapid environmental change from river to marsh occurred in the end of the 15th century. Migration of volumes of * 茨 :o.fujiwara@aist.go.jp Present address: Department of Geography, Nara University,1500 Misasagi-cho, Nara, , Japan ** Present address: Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University, , Hakozaki, Higashi-ku, Fukuoka, , Japan

Nishi-ku, Niigata, 950-2181, Japan Toshifumi YATA Faculty of Humanities, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, 950-2181, Japan Masatomo UMITSU, Yoshiki SATO ** Graduate

2 sediments caused by the Meio tsunami is a possible source of the river mouth closure. This environmental change was synchronous with the sudden decline of a famous port town, Hashimoto, flourished along the Hamana River. Break off of the water route connecting the Hashimoto and Pacific Ocean potentially led to the decline and removal of the port town. Keywords: Enshu-nada, Hamana River, Nankai Trough, 1498Meio earthquake, Tsunami M 灘 Komatsubara et al., 2008 灘灘 m 4 m 4.8 m 灘 m m m B m 灘 1 B No m 100 mm

Break off of the water route connecting the Hashimoto and Pacific Ocean potentially led to the decline and removal of the port town.

3 ARI-1 ARI m 100 mm 1B ARI-5 m ARI-5 ARI-5-2 ARI-6 15 m ARI-6 ARI-6-2 Takada and Atwater AMS 14 C OxCal3.10 (Ramsey, 1995, 2001) IntCal04 (Reimer et al., 2004) Marine04 (Hughen et al., 2004) 400 ( ΔR= 0) C No No m A ( 1946 ) B:. 1/25,000 Fig. 1 Index map. A: Topography around the study area in 1946 (Aerial photographs were taken by the Far East Air Force). B: Map showing the study area and excavation sites ( Geoslicer, Drilling). Modified from 1/25,000-scale topographic map Araimachi of Geographical Survey Institute

02 m 2 3 1 A ( 1946 ) B:. 1/25,000 Fig. 1 Index map.

4 1991 ARI-5 ARI-6 No No m m 15 cm Lining cm Corbicula japonica) Soletellina? sp. 僅 90 cm 2 3 No.1 ARI m ARI m 3 ARI-5-2 Lining 5 No.8, 9, 12, 13, AD(No.13) AD No.17 No.1 Fig. 2 Photograph showing the Core Arai No.1. The section below the elevation of m (Late Pleistocene sand beds) is omitted

7 m ARI-6-0.35 m 3 ARI-5-2 Lining 5 No.8, 9, 12, 13, 17 800-980AD(No.13) 1340-1400AD No.

5 Lining 1997 Psilonichnus isp. ARI-6, No.1 ARI-5 3 ( ) No.1 No.1 3 No m 1 Fig. 3 Columnar section of the cores and calibrated 14 C ages. The section below the elevation of m in the Core Arai No.1 is omitted. Calibrated ages underlined in the Table 1, which have the highest probability distribution, are shown in this figure. Calibrated ages (2σ age range) in the parenthesis are from the closest cores that are shown in the Appendix

6 1 14 C Table C ages from study area. Ages with the highest probability distribution are underlined. δ 13 C 14 C (AD) yrbp±1σ PLD- 1σ 2σ ± ± (68.2%) (95.4%) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ( 8.7%) (39.8%) ( 7.6%) (12.1%) (43.6%) (24.6%) (26.1%) (41.2%) (0.9%) (1.4%) (66.8%) (11.1%) (33.6%) (8.5%) (15.0%) (52.2%) (16.0%) (31.6%) (10.7%) (25.8%) (43.0%) (25.2%) (18.7%) (6.8%) (34.7%) (8.0%) (16.2%) (53.5%) ( 6.8%) (18.9%) (63.3%) (32.1%) (37.5%) (45.3%) (12.6%) (19.6%) (72.7%) ( 3.1%) (16.1%) (46.7%) (14.6%) (18.0%) (66.7%) (28.7%) (95.4%) (95.4%) (28.0%) (67.4%) ± ± Corbicula japonica Soletellina? sp ± ± ±0.16 0± ± ± ± ± ± ± (54.5%) (13.7%) (27.0%) (41.2%) (95.4%) (95.4%) ± ±25 835(68.2%) (95.4%) (20.3%) (33.6%) (14.4%) (53.4%) (14.8%) (45.3%) (22.9%) (27.1%) (41.1%) (30.2%) (47.4%) (17.9%) (95.4%) ( 6.9%) (88.5%) (41.3%) (54.1%)1400 ARI-6 2 3,

43-21.97±0.13 895±25 9 10057-1.01-25.79±0.12 920±25 10 9250 0.36-14.38±0.15 120±20 1670( 8.7%)1690 1730(39.8%)1780 1790( 7.6%)1810 1920(12.1%)1950 1520(43.6%)1560 1630(24.6%)1650 1650(26.

7 ARI-6 No cm 7 No.6, 7, 10, 11, 14, 15, 16 No AD(No.7) 溢 ARI-1 ARI cm 70 cm ARI-4 5cm 5 No.1 5 No AD No.17 No AD(No.7) 灘 No.2-7, 11, 14, Komatsubara et al., 灘

1 5 No.1 1500-1600 5. 5.1 1340-1400AD No.17 No.1 1440-1530AD(No.7) 灘 No.

8 , No.1 遡灘灘 6 灘灘 C B : pp., with 5 plates pp pp Hughen, K. A., Baillie, M. G. L., Bard, E., Beck, J. W., Bertrand, C. J. H., Blackwell, P. G., Buck, C. E., Burr, G. S., Cutler, K. B., Damon, P. E., Edwards, R. L., Fairbanks, R.G., Friedrich, M., Guilderson, T. P., Kromer, B., McCormac, G., Manning, S., Ramsey, C. B., Reimer, P. J., Reimer, R. W., Remmele, S., Southon, J. R., Stuiver, M., Talamo, S., Taylor, F. W.; van der Plicht, J., Weyhenmeyer, C. E., 2004, Marine04 marine radiocarbon age calibration, 0 26 cal kyr BP. Radiocarbon, 46, Komatsubara, J. Fujiwara, O., Takada, K., Sawai, Y., Than T. Aung and Kamataki, T., 2008, Historical tsunamis and storms recorded in a coastal lowland, Shizuoka prefecture, along the Pacific Coast of Japan. Sedimentology, 55,

, Ramsey, C. B., Reimer, P. J., Reimer, R. W., Remmele, S., Southon, J. R., Stuiver, M., Talamo, S., Taylor, F. W.; van der Plicht, J., Weyhenmeyer, C. E.

9 No Psilonichnus Ramsey, C. B., 1995, Radiocarbon calibration and analysis of stratigraphy: The OxCal program. Radiocarbon, 37, Ramsey, C. B., 2001, Development of the radio- carbon program OxCal. Radiocarbon, 43, Reimer, P. J., Baillie, M. G. L., Bard, E., Bayliss, A., Beck, J. W., Bertrand, C. J. H., Blackwell, P. G., Buck, C. E., Burr, G. S., Cutler, K. B., Damon, P. E., Edwards, R. L., Fairbanks, R. G., Friedrich, M., Guilderson, T. P., Hogg, A. G., Hughen, K. A., Kromer, B., Mc- Cormac, G., Manning, S., Ramsey, C. B., Reimer, R. W., Remmele, S., Southon, J. R., Stuiver, M., Talamo, S., Taylor, F. W., van der Plicht, J. and Weyhenmeyer, C. E., 2004, IntCal04 terrestrial radiocarbon age calibration, 0 26 cal kyr BP. Radiocarbon, 46, , pp, 1991, Takada, K. and Atwater, B. F., 2004, Evidence for Liquefaction identified in peeled slices of Holocene deposits along the lower Columbia River, Washington. Bull. Seismol. Soc. Ameri. 94, (Handy Geoslicer), no. 579, pp 2003 [416] pp, 2005, , 2009, 203pp

L., Fairbanks, R. G., Friedrich, M., Guilderson, T. P., Hogg, A. G., Hughen, K. A., Kromer, B., Mc- Cormac, G., Manning, S., Ramsey, C. B., Reimer, R. W., Remmele, S., Southon, J. R., Stuiver, M.

10 Appendix 1 Columnar section of the core and calibrated 14 C ages. Calibrated ages underlined in the Table 1, which have the highest probability distribution, are shown in this figure. Not in scale with horizontal distance

熊本大学学術リポジトリ Kumamoto University Repositor Title 阿蘇火山米塚の噴火年代 Author(s) 宮縁, 育夫 Citation 火山, 55(5): Issue date Type URL Right Journal

熊本大学学術リポジトリ Kumamoto University Repositor Title 阿蘇火山米塚の噴火年代 Author(s) 宮縁育夫 Citation 火山 55(5): 219-225 Issue date 2010-10-31 Type URL Right Journal Article http://hdl.handle.net/2298/37047 2010 特定非営利活動法人日本火山学会