The Philippine Sea plate subducts beneath the Eurasia plate at the Nankai Trough, northwestern Pacific, causing crustal deformation, mega-thrust earthquakes, and tsunami events. Shikoku Island, 150 km northwest of the trough, experiences both coseismic and interseismic deformation. Coastal sediments potentially record vertical crustal movements as relative sea level (RSL) changes. We studied sedimentary facies and microfossil ostracodes in core SKM from southwestern Shikoku Island for evidence of middle Holocene tsunami events and deformation. The core sediments included nine event layers corresponding to storm or tsunami events. Using modern analog techniques, we estimated RSLs from the ostracode assemblages of core SKM and 13 other cores from Shikoku Island and the surrounding region. Then, we subtracted RSL changes due to glacio-hydro isostatic adjustment from the estimated RSLs to estimate vertical tectonic movement rates in these cores between 8.6 and 4.7 ka. The inferred RSL changes suggest that the Sukumo site has experienced both uplift and subsidence since 8.6 ka. Before 6.6 ka, rates of the tectonic crustal movement were higher than the modern-day rate, and its spatial distribution also differed. After 6.6 ka, the tectonic crustal movement showed a similar spatial pattern and occurred at rates close to the modern-day interseismic rate. The spatial pattern and rates of tectonic crustal movement could be caused by changes in rupture areas between Eurasia and the Philippine Sea plates beneath Shikoku Island and in stress conditions of the asthenosphere.  Some of the vertical displacements can be explained by the movements of local active faults.

The modern data (i.e. the training data) for the modern analogous technique consist of 341 samples and 574 taxa (Modern_data.csv). Each sample has at least 50 ostracodes. The water depth of the modern data ranges from 0.3 to 50 m (Modern_data_WD_Coord.csv). To organize the data, we selected and complied ostracode census data tagged with water depth to corelate with the census ostracode data in 25 bays of the Japanese coasts (Modern_data_localities.pdf), referring to 27 studies (Bodergat and Oki, 2020; Frydl, 1982; Ikeya and Hanai, 1982; Ikeya and Suzuki, 1992; Irizuki et al., 2003, 2006, 2008, 2009, 2018; Ishizaki, 1968, 1969, 1971; Itoh, 1998; Kamiya et al., 2001; Kawano et al., 2013; Masuma and Yamada, 2014; Tanaka, 2008; Tanaka et al., 2019; Tsukawaki et al., 1997, 1998, 2000; Yamane, 1998; Yasuhara and Irizuki, 2001; Yasuhara et al., 2002, 2005; Yasuhara and Seto, 2006). In taxonomy of the data, we merged a species compared to a described species, that has “cf.” in scientific name to the described species and lumped Microcythere, Neocytherideis, Paradoxostoma,Pseudocythere, Sclerochilus, Sulcocytherura, Triebelina, and Xiphichilusspecies to each genus. The taxonomic names in the data files are abbreviated as Codes, that are referred to Taxon_references.csv. 

References

Bodergat, A.-M., Oki, K., 2020. Ostracods surface species in Kagoshima Bay and their distribution. Nature of Kagoshima 46, in press. 
Frydl, P.M., 1982. Holocene ostracods in the southern Boso Peninsula, in: Hanai, T. (Ed.), Studies on Japanese Ostracoda, Bulletin, University Museum, University of Tokyo. University of Tokyo, Tokyo, pp. 61–140, 257–267.
Ikeya, N., Hanai, T., 1982. Ecology of recent ostracods in the Hamana-ko region, the Pacific coast of Japan, in: Hanai, T. (Ed.), Studies on Japanese Ostracoda, Bulletin, University Museum, University of Tokyo. pp. 15–59.
Ikeya, N., Suzuki, C., 1992. Distributional patterns of modern ostracodes off Shimane, southwestern Japan Sea. Rep. Fac. Sci. Shizuoka Univ. 26, 91–137.
Irizuki, T., Fujihira, Y., Iwatani, H., Kawano, S., 2018. Recent ostracode assemblages from Shushi Bay, Tsushima Island, southwestern Japan and their ecological and zoogeographical characteristics. Laguna 25, 39–54.
Irizuki, T., Gotomyo, A., Kawano, S., Yoshioka, K., Nomura, R., 2009. Relationships between Recent ostracode assemblage and environmental factors in the northern part of Harima-nada Bay off Aioi City, Hyogo Prefecture, Southwest Japan. Geosci. Rep. Shimane Univ. 28, 1–9. [in Japanese with English abstract]
Irizuki, T., Ito, H., Yoshioka, K., Kawano, S., Nomura, R., Tanaka, Y., Sako, M., 2010. Recent ostracode assemblages and the marine environment around Kasado Bay in northeastern Suo-nada Bay, Yamaguchi Prefecture, Southwest Japan. Geosci. Rep. Shimane Univ. 29, 11–20. [in Japanese with English abstract]
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Ishizaki, K., 1969. Ostracodes from Shinjiko and Nakanoumi, Shimane Prefecture, Western Honshu, Japan. Sci. Reports Tohoku Univ. Sendai, Second Ser. 41, 197–224.
Ishizaki, K., 1968. Ostracodes from Uranouchi Bay, Kochi Prefecture, Japan. Sci. reports Tohoku Univ. Second Ser. Geol. 43, 59–97.
Itoh, H., 1998. Ostracode assemblages from Lake Hamana, Shizuoka Prefecture, Japan in 1996. Laguna 5, 93–99. [in Japanese with English abstract]
Kamiya, T., Ozawa, H., Obata, M., 2001. Quaternary and Recent marine Ostracoda in Hokuriku district, the Japan Sea coast, in: Ikeya, N. (Ed.), Guidebook of Excursions, the 14th International Symposium of Ostracoda. Organising Committee of ISO, Shizuoka, pp. 73–106.
Kawano, S., Irizuki, T., Nomura, R., 2013. Temporal changes of recent ostracode assemblages and bay environment with relation to the opening and extension of the Manzeki-seto Strait in the Tsushima Island, southwest Japan. Earth Sci. (Chikyu Kagaku) 67, 89–99. [in Japanese with English abstract]
Masuma, T., Yamada, K., 2014. Recent ostracode distributions in Kumihama Bay ( brackish lake ) in the northern part of Kyoto Prefecture, central Japan. Laguna 21, 1–14. [in Japanese with English abstract]
Tanaka, G., 2008. Recent benthonic ostracod assemblages as indicators of the Tsushima warm current in the southwestern sea of Japan. Hydrobiologia 598, 271–284. doi:10.1007/s10750-007-9162-6
Tanaka, G., Henmi, Y., Masuda, T., Moriwaki, H., Komatsu, T., Zhou, B., Maekawa, T., Niiyama, S., Nguyen, P.D., Doan, H.D., Ikeya, N., 2019. Recent ostracod distribution in western Kyushu, Japan, related to the migration of Chinese continental faunal elements. Mar. Micropaleontol. 146, 1–38. doi:10.1016/j.marmicro.2018.12.002
Tsukawaki, S., Kamiya, T., Kato, M., Matsuzaka, T., Naraoka, H., Negishi, K., Ozawa, H., Ishiwatari, R., 1997. Preliminary results from the R.V. Tansei-maru Cruise KT95-14 Leg 2 in the southern marginal area in the Japan Sea–Part 1: Sediments, benthic foraminifers and ostracodes. Bull. Japan Sea Res. Inst. 13–43.
Tsukawaki, S., Kamiya, T., Ozawa, H., Kato, M., 1998. Preliminary results from the R.V. Tansei-maru Cruise KT96-17 Leg 2 in the southwestern part of the Japan Sea–Sediments, benthic foraminifers and ostracodes. Bull. Japan Sea Res. Inst. 67–89.
Tsukawaki, S., Ozawa, H., Domitsu, H., Kamiya, T., Kato, M., Oda, M., 2000. Preliminary results from the R.V. Tansei-maru Cruise KT98-17 in the southern marginal part of the Japan Sea–Sediments, benthic and planktonic foraminifers, and ostracodes. Bull. Japan Sea Res. Inst. 89–119.
Yamane, K., 1998. Recent ostracode assemblages from Hiuchi-nada Bay, Seto Inland Sea of Japan. Bull. Dep. Nat. Hist. Ehime Pref. Sci. Museum 3, 19–59. [in Japanese with English abstract]
Yasuhara, M., Irizuki, T., 2001. Recent Ostracda from the northeastern part of Osaka Bay, southwestern Japan. J. Geosci. Osaka City Univ. 44, 57–95.
Yasuhara, M., Irizuki, T., Yoshikawa, S., Nanayama, F., 2002. Change in Holocene ostracode faunas and depositional environments in the Kitan Strait, Sothwestern Japan. Paleontol. Res. 6, 85–99.
Yasuhara, M., Seto, K., 2006. Holocene relative sea-level change in Hiroshima Bay, Japan: a semi-quantitative reconstruction based on ostracodes. Paleontol. Res. 10, 99–116.
Yasuhara, M., Yoshikawa, S., Nanayama, F., 2005. Reconstruction of the Holocene seismic history of a seabed fault using relative sea-level curves reconstructed by ostracode assemblages : Case study on the Median Tectonic Line in. Palaeogeogr. Palaeoclimatol. Palaeoecol. 222, 285–312. doi:10.1016/j.palaeo.2005.03.019

Modern_data.csv and Modern_data_WD_Coord.csv are dataset to perform the modern analogue technique, using R and its software package “analgoue”.