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前缘地区，该地区有记录在案的过去2000年来多次大地震和海啸的历史。因此，目前它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，但南开拥有比这两个美国例子都广泛得多的数据库。这项研究将提供信息，帮助理解俯冲带沉积物厚度和类型的变化如何影响破坏性地震的发生，以及哪些地震可能引发海啸。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，而且在世界各地的其他俯冲带上也是如此。这项研究是与日本海洋地球科学技术厅(JAMSTEC)合作进行的。该项目支持对一名美国研究生的培训。该项目是夏威夷大学和日本海洋地球科学技术厅(JAMSTEC)的合作项目。将对横跨南开海槽中西部增积棱镜的新的JAMSTEC高分辨率地震反射资料进行处理和解释。南开海槽增积棱柱可以说是世界上研究最深入的沉积控制边缘，因此是典型的例子。因此，南开地区一直是众多研究的焦点，包括JAMSTEC沿着整个系统收集跨变形前锋的高分辨率地震反射线的新努力。这项研究将把新的解释与两个三维地震和钻井断面的现有数据以及JAMSTEC沿断面和断面之间的所有可用地球物理数据结合起来，特别是多道地震反射、海底地震仪、多波束测深和甚低频地震活动数据。其目的是了解沉积物厚度、洋壳地形和棱柱头变形结构的区域变化之间的相互关系。这项工作将检验这样一种假设，即俯冲地形，即使是相对较小的不规则性，如小海山，也会导致俯冲半深海和上覆海沟浊积岩沉积段的厚度变化。这导致了原始冲断带(PTZ)内厚度和宽度的变化，以及叠瓦状冲断带(ITZ)内山脊的不连续。较大的海山和断裂带俯冲，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地区性变化是否与更深层次特征的变化相关，如慢滑地震。

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.