Quantitative assessment of deformation of upper crust based on paleomagnetism of widespread tephra and large-scale pyroclastic flow deposit

基于广泛分布的火山灰和大型火山碎屑流沉积的古地磁定量评估上地壳变形

基本信息

批准号：
17540438
负责人：
ITOH Yasuto
金额：
$ 2.24万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540438/
关键词：
geophysics natural disaster earthquake paleomagnetism active fault geodesy geology disaster prevention

项目摘要

In this study, field survey was conducted for widespread tephra, large-scale pyroclastic flow deposits and a Quaternary volcano in the central part of Honshu Island, Japan. Samples for paleomagnetic measurements were obtained from 39 sites. Remanent magnetization was measured by a spinner magnetometer, and stability of remanence was evaluated by progressive thermal and alternating-field demagnetization. Progressive acquisition of isothermal remanent magnetization (IRM) was conducted using a pulse magnetizer in order to estimate ferromagnetic minerals in rocks, and the estimation was verified through thermal demagnetization of orthogonal IRM. Available site-mean paleomagnetic directions were compiled for determination of high strain area, which was correlated with a deformation zone recently detected through geodetic studies of nationwide GPS array. Along with these study, fault motion and basin-forming history over 10 m.y. in an arc-arc junction (Hokkaido) and a seismogenic subduction zone (Pacific coast of northeast Japan) were clarified on the basis of interpretation of reflection seismic data, which gave a significant clue to understand tectonics in central Japan. We have precisely assessed short-term crustal deformation utilizing paleomagnetic method, which is generally applied for long-standing cumulative deformation between plates.

在这项研究中，对广泛的tephra，大规模的火山碎屑流沉积物和日本洪斯岛中部的第四纪火山进行了现场调查。从39个地点获得了古磁测量的样品。通过旋转器磁力计测量了远程磁化强度，并通过进行性热和交流场去电磁来评估re漫画的稳定性。为了估算岩石中的铁磁矿物质，对等温远离磁化（IRM）进行了逐步恢复，并通过正交IRM的热消电效应来验证估计。编译了可用的现场均匀古磁方向，以确定高应变面积，这与最近通过全国GPS阵列的大地测量研究检测到的变形区有关。除这些研究外，断层运动和盆地形成历史超过10 M.Y.在解释反射地震数据的基础上，阐明了在ARC-ARC交界处（北海道）和地震俯冲区（日本东北太平洋海岸）中，这给出了重要的线索，以了解日本中部的构造。我们已经使用古磁方法精确地评估了短期地壳变形，这通常用于板之间的长期累积变形。