Reconstruction of paleoseismic history in the Nankai Trough Zone by analyzing Holocene raised limestones

全新世隆起灰岩分析重建南海海槽带古地震历史

• 批准号: 13680103
• 负责人: MAEMOKU Hideaki
• 金额: $ 1.66万
• 依托单位: Hiroshima University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13680103/
• 关键词: Nankai Earthquake; Cape Muroto; coseismic uplift; sessile organism; paleo depth of water; carbonate structure; limestone

This study aims to elucidate paleoseismic history in the Nankai Trough Zone by using Holocene raised limestones attached to coastal rocks. Sedimentological study was conducted on Holocene limestone that occurs along the coast from Cape Muroto to Meoto-iwa located about 13 km to the north of the cape. Distribution of the limestone is limited to <10 m in elevation. The limestone is up to 4.4 meter in mean diameter and less than 0.5 m in thickness, and consists mainly of fossilized sessile organisms such as annelids, bryozoans, corals, encrusting foraminifera, and coralline algae. Associated components include barnacles, ostracods, molluscs, echinoids, benthic foraminifera, peyssonneliacean algae, and non-calcareous clasts and grains. Cement is a minor component and found in a semi-closed space between coralline algal crusts and their substrates. Modal composition of limestone was determined by a point counting technique. The results show that the limestone can be classified into 6 types on the basis of predominant fossilized sessile organisms. The dominant components are : corals and coralline algae in Type I ; coralline algae in Type II ; coralline algae, annelids and barnacles in Type III ; coralline algae and annelids in Type IV ; encrusting foraminifera and encrusting bryozoans in Type V ; and molluscs in Type VI. Comparison of vertical distribution of the six types with those of modern sessile organisms indicates the highest elevation of Type I at a particular outcrop corresponds to mean low sea level (MLSL) when the limestone formed. Therefore the Holocene limestone is considered ideal for the analysis of relative sea-level changes.

本研究旨在利用附着在沿海岩石上的全新世隆起石灰岩来阐明南海海槽带的古地震历史。对从室户岬到位于岬以北约 13 公里的夫妻岩沿岸的全新世石灰岩进行了沉积学研究。石灰岩的分布仅限于海拔<10 m的范围内。石灰岩平均直径达4.4米，厚度不足0.5米，主要由环节动物、苔藓虫、珊瑚、有壳有孔虫、珊瑚藻等固着生物化石组成。相关成分包括藤壶、介形类、软体动物、海胆类、底栖有孔虫、佩松藻类以及非钙质碎屑和谷物。水泥是一种次要成分，存在于珊瑚藻结皮与其基质之间的半封闭空间中。石灰石的模态组成通过点计数技术测定。结果表明，根据主要的固着生物化石，石灰岩可分为 6 类。主要成分为： I型珊瑚和珊瑚藻； II 型珊瑚藻； III 型珊瑚藻、环节动物和藤壶； IV 型珊瑚藻和环节动物； V型包壳有孔虫和包壳苔藓虫；和 VI 型软体动物。将六种类型的垂直分布与现代固着生物的垂直分布进行比较表明，特定露头的 I 型最高海拔对应于石灰岩形成时的平均低海平面（MLSL）。因此，全新世石灰岩被认为是分析相对海平面变化的理想选择。

项目成果

前杢 英明: "隆起付着生物のAMS14C年代からみた室戸岬の地震性隆起に関する再検討"地学雑誌. 110. 479-490 (2001)

Hideaki Maemoku：“从 AMS14C 时代的隆升附着生物重新审视室户岬的地震隆起”地质杂志 110. 479-490 (2001)。

前杢 英明: "隆起付着生物のAMS ^C年代からみた室戸岬の地震性隆起に関する再検討"地学雑誌. 110・4. 479-490 (2001)

Hideaki Maemoku：“从AMS ^<14>C年龄的隆起生物的角度重新审视室户岬的地震隆起”地质杂志110・4（2001）。