著者

宍倉 正展 越後 智雄 行谷 佑一

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2020, no.53, pp.33-49, 2020-12-25 (Released:2021-07-11)

参考文献数

25

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Marine terraces (probably Holocene terraces) divided into three levels of L1 to L3, representing the activity of off-shore active faults, have been developed along the northern coast of the Noto Peninsula, central Japan. To evaluate the mean vertical displacement rate and recurrence interval of off-shore active faults, this study tries to estimate the emergence age of terraces using an idea of time predictable model with the rate of relative sea-level fall. In the Saruyama-oki segment off the northwestern coast, assuming the ages of the L1 terrace to be 6,000 or 3,500 years ago based on previously reported peak age of post-glacial transgression, it is inferred that the mean vertical displacement rate is 0.87 mm/year or 1.49 mm/year, and recurrence interval is 2,000 or 1,200 years. However, the emerged sessile assemblages indicate the shortest interval of 300 years because the height and age suggest that two uplift events of 0.7 m and 0.8 m occurred in the 9th century and 12th to 13th centuries, respectively. In the Wajima-oki and Suzu-oki segments off the north-central to northeastern coast, the height distribution of the lower terraces indicates undulating deformation with two peaks, which is consistent with the height distribution of the late Pleistocene terrace. This suggests the characteristic displacement and its accumulation due to the fault activity of these segments. Under the same assumptions for estimating the age of terraces, the mean vertical displacement rate and recurrence intervals are 0.67-0.72 mm/year or 1.14-1.23 mm/year and 900-1,400 years or 500-800 years respectively. The age of emerged sessile assemblage indicates that the latest event of the Wajima-oki segment can be correlated to the historical earthquake of AD 1729.