Expedition Oriented Research: Sedimentation and tectonics in Kumano forearc basin evolution, NantroSEIZE study area

许多破坏性俯冲带地震孕育在增生棱柱上方的沉积弧前盆地之下。这样的行为肯定是日本附近的南开棱镜的特征--S半岛，熊野盆地位于一个无序的或可能发生地震的巨型断层之上。南开棱柱的行为在很大程度上受前缘逆冲系统、进海沟-沉积物和解冻带的控制。然而，斜坡和弧前盆地过程对边缘的机制也可能是重要的。由于IODP 315、316和319探险期间的钻探，有可能在以前无法达到的水平上研究弧前盆地的演化。IODP钻探揭示，熊野盆地的底部与上新世-更新世边界大致重合，这增加了沉积模式的变化影响弧前盆地启动的可能性。提出了一种假设，即从沟进沉积到前缘增积棱柱再到腹地进积斜坡和弧前盆地沉积模式的变化与沉积楔体力学的变化相吻合。如果气候控制的沉积模式确实在很大程度上控制了南开边缘的构造，这将为气候驱动的沉积物通量与构造变形之间存在争议的联系提供一个很好的例子。我们将在边际演化模型的背景下测试我们的假设。我们的模型预测，在上新世-更新世从低到高沉积通量的转变过程中，南开棱柱沿线发育了无序逆冲和斜坡盆地，以努力使楔体恢复到临界锥度。内部的楔形变形最终形成了早期的弧前盆地。在更新世，日本阿尔卑斯山的隆升导致大量的沉积物流向楔形体的脚趾，导致增积棱柱向海推进，沉积物向下逆冲，形成巨型沉积。中更新世以后更大的沉积物通量导致熊野盆地的快速充填和孕震板块边界的加载。我们将使用三维地震反射数据的运动学恢复、井下和岩心对构造方向和倾斜史的约束、关键剖面的沉积物源和库仑楔体解析解来评估这一描述性模型的关键组成部分。日本？S南开吸积棱柱是1944年和1946年大地震的发源地。我们的工作将为NantroSEIZE实验生成所需的数据集，该实验旨在研究和监测弧前盆地以下的地震变形，与棱镜-S脚趾附近的主要非地震变形形成对比。拟议的研究重点对GeoPRISMS计划非常感兴趣，导致了跨NSF计划的影响。我们将与日方同仁结成伙伴，提升国际影响力。我们的教育和外展活动将通过支持一名研究生，并根据我们的研究生成学习模块。这些模块将建立在现有的本科教程的基础上，并针对德克萨斯大学奥斯汀分校的项目进行额外的定制，以迎合以少数族裔为主的公立学校教师的需求，从而提高国内公众对地质过程和自然灾害的认识。

Many destructive subduction-zone earthquakes nucleate beneath the sedimentary forearc basins above accretionary prisms. Such behavior certainly characterizes the Nankai prism off Japan?s Kii Peninsula where the Kumano basin sits above an out-of-sequence, or megasplay fault that is likely seismogenic. Nankai-prism behavior is largely governed by the frontal thrust system, incoming trench-sediment, and décollement zone. Yet, slope and forearc basin processes are also likely important to the mechanics of the margin. Because of drilling during IODP Expeditions 315, 316, and 319, it is possible to examine forearc basin evolution at a level not previously attainable. IODP drilling has revealed that the base of the Kumano basin roughly coincides with the Plio-Pleistocene boundary, raising the possibility that a change in sedimentation patterns affected forearc basin initiation. It is proposed to test the hypothesis that changes in sedimentation patterns from trench-fed sediment into the frontal accretionary prism to hinterland-fed slope and forearc basin deposition, coincide with changes in accretionary wedge mechanics. If climate-controlled sedimentation patterns do exert a large control on the Nankai margin tectonics, it would provide a good example of the controversial link between climate-driven sediment flux and tectonic deformation. We will test our hypothesis in the context of a margin-evolution model. Our model predicts that during the Plio-Pleistocene transition from low-to-high sediment flux, out-of-sequence thrusts and slope-basins developed along the Nankai prism in an effort to return the wedge to critical taper. The internal wedge deformation ultimately formed an incipient forearc basin. During the Pleistocene, uplift of the Japanese Alps caused significant sediment flux to the toe of the wedge and resulted in seaward advance of the accretionary prism, sediment underthrusting, and formation of the megasplay. Even greater sediment flux after the Mid-Pleistocene resulted in rapid infilling of the Kumano Basin, and loading of the seismogenic plate boundary. We will evaluate the key components of this descriptive model using a kinematic restoration of 3-D seismic reflection data, down-hole and core constraints on structural orientation and tilting histories, sedimentary provenance of key sections, and Coulomb wedge analytical solutions.Japan?s Nankai accretionary prism is the site of the 1944 and 1946 great earthquakes. Our work will generate needed datasets for the NantroSEIZE experiment, which seeks to study and monitor seismic deformation below the forearc basin, in contrast with predominantly aseismic deformation near the prism?s toe. The focus of the proposed research is of great interest to the GeoPRISMS program, leading to cross NSF programmatic impact. We will partner with Japanese colleagues, enhancing the international impact. Our education and outreach activities will be through support of a graduate student, and generating learning modules from our research. These modules will build on existing undergraduate tutorials, and be additionally tailored to UT-Austin programs that cater to predominantly minority-serving public school teachers, thereby increasing domestic public awareness about geological processes and natural hazards.