Variations in Deformational Style at the Toe of the Nankai Accretionary Prism: Relation to Subducting Plate Sediment Thickness and Basement Topography

该项目旨在帮助了解日本南开俯冲带的锋面区域，该地区在过去2000年里有许多大地震和海啸的记录。因此，它目前被认为受到地震和海啸的威胁。南开俯冲带在许多方面与卡斯卡迪亚和阿留申俯冲带相似，但南开的数据库比这两个美国的例子都要广泛得多。这项研究将提供有助于了解沿俯冲带的沉积物厚度和沉积物类型的变化如何影响破坏性地震的发生以及哪些地震可能产生海啸的信息。这项工作还将有助于了解破坏性地震的区域范围和潜在时间，不仅在日本，而且在世界范围内的其他俯冲带。这项研究是与日本海洋地球科学技术机构（JAMSTEC）合作进行的。该项目支持培训一名美国研究生。该项目是夏威夷大学和日本海洋地球科学技术机构（JAMSTEC）之间的合作成果。新的JAMSTEC高分辨率地震反射数据将跨越南开海槽中部和西部的增生棱镜进行处理和解释。南开海槽增生三棱镜可以说是世界上研究得最好的以沉积为主的边缘，因此可以作为典型的例子。因此，南开地区一直是众多研究的焦点，包括JAMSTEC在整个系统变形前沿收集高分辨率地震反射线的新努力。该研究将把新的解释与两个三维地震和钻井样带的现有数据以及样带沿线和之间的所有可用JAMSTEC地球物理数据结合起来，特别是多通道地震反射、海底地震仪、多波束测深和甚低频地震活动数据。目的是了解沉积物厚度的区域变化、海洋地壳地形和棱镜趾部变形结构之间的相互关系。这项工作将检验俯冲地形的假设，即使是相对较小的不规则现象，如小海山，也会导致俯冲半深海和上覆海沟浊积岩沉积剖面的厚度变化。这导致原始逆冲带（PTZ）内厚度和宽度的变化以及叠瓦状逆冲带（ITZ）内山脊的不连续。较大海山和断裂带的俯冲作用，沉积物厚度变化较大，导致PTZ和ITZ的区域结构变化。该项目还旨在确定这些区域变化是否与深层特征（如慢滑地震）的变化相关。

This project is designed to help understand the frontal region of the Nankai subduction zone off of Japan, an area that has a documented history of many great earthquakes and tsunami in the past 2000 years. As such, it is currently believed to be endangered by earthquake and tsunami hazards. The Nankai subduction zone is similar in many ways to both the Cascadia and Aleutian subduction zones, but Nankai has a much more extensive data base than either of these U.S. examples. This study will provide information that will help to understand how variations in sediment thickness and type of sediment along subduction zones influence the occurrence of destructive earthquakes and which earthquakes might generate tsunami. The work also will help to understand the regional extent and potential timing of destructive earthquakes not only in Japan, but also along other subduction zones worldwide. This study is in collaboration with the Japan Agency for Marine Earth Science and Technology (JAMSTEC). The project supports the training of a U.S. graduate student. This project is a collaborative effort between the University of Hawaii and the Japan Agency for Marine Earth Science and Technology (JAMSTEC). New JAMSTEC high-resolution seismic reflection data across the central and western Nankai Trough accretionary prism will be processed and interpreted. The Nankai Trough accretionary prism is arguably the best-studied sediment-dominated margin in the world, and thus serves as the type example. As such, the Nankai region has been the focus of numerous studies, including the new effort by JAMSTEC to collect high-resolution seismic reflection lines across the deformation front along the entire system. This study will integrate new interpretations with existing data from two 3D seismic and drilling transects along with all available JAMSTEC geophysical data along and between the transects, especially multichannel seismic reflection, Ocean Bottom Seismograph, multibeam bathymetry and Very Low Frequency seismicity data. The goal is to understand the inter-relations between regional variations of sediment thickness, oceanic crust topography, and deformational structures at the toe of the prism. The work will test the hypothesis that subducting topography, even relatively small irregularities such as small seamounts, causes thickness variations in the subducting hemipelagic and overlying trench turbidite sedimentary sections. This leads to variations in thickness and width within the proto-thrust zone (PTZ) and to discontinuities in ridges within the imbricate thrust zone (ITZ). Subduction of larger seamounts and fracture zones, with greater variations in sediment thickness, cause regional structural variations in the PTZ and ITZ. The project is also designed to determine whether or not these regional variations are correlated with variations in deeper features such as slow slip earthquakes.