Collaborative Research: Numerical Modeling of Fluid Flow and Transport during out of Sequence Thrusting and Underplating: Application to the NanTroSEIZE Investigation Area

了解逆序逆冲、流体排出、底板和板块边界断裂行为之间的相互作用对南开海槽发震带实验（NanTroSEIZE）具有重要意义，但这些过程尚未通过流体流动和变形模拟进行研究。因此，本建模研究将解决这些主要过程对棱镜内孔隙压力和流体流动的影响，大展布断层和板块边界断层。建模将使用现有的软件包ABAQUS来实现。该软件包提供了模拟该建模的主要特征的能力，将允许其他研究人员重现建模结果，并且足够灵活以适应未来俯冲带建模的需求。该模型将应用于南开俯冲带的Kii样带，并用于验证以下相关假设：假设1：大展布断裂系统显著改变了增生杂岩内的超孔隙压力和孔隙损失模式。假设2：通过对孔隙压力、孔隙度和流体化学的观察，可以阐明南开大张开系统的水文作用。假设3：通过将沉积物转移到不同的应力状态，并将滑脱带移动到脱水较少的区域，海底沉积使增生棱镜底部的流体排出恢复活力。虽然该模型仅应用于南开俯冲杂岩的Kii样带，但对于其他俯冲带以及褶皱带和冲断带的工作人员来说，底板和逆序冲断对俯冲带脱水和变形的重要性的评估将是有用的。在许多俯冲带中，扇形断裂和底板是可以极大地改变孔隙压力和孔隙度分布（从而改变地震发生）的通常推断特征。更广泛的影响了解发震带过程对地震和海啸灾害具有重大的社会影响。这项研究将是对发震带进行长期研究的第一步。在调查过程的早期进行建模可以帮助在钻井和监测过程中制定科学的策略。ABAQUS软件包的使用将扩展俯冲带建模社区的能力。模型输入数据集将提供给其他研究人员。作为NanTroSEIZE的积极支持者，Liz Screaton将在未来的研讨会和与NanTroSEIZE相关的会议上直接与其他支持者交流建模结果。此外，普遍关注的结论将在科学期刊上发表，并在国家科学会议上提出。这个项目将培养研究生。在佛罗里达大学，它将适用于一名博士或两名硕士学生。在科罗拉多大学，项目工作将涉及一名学生（硕士或博士）的建模。研究生将出席科学会议，该项目将是他们的论文或论文的重要组成部分。

Understanding the interplay between out-of-sequence thrusts, fluid expulsion, underplating, and the behavior of the plate boundary fault is of fundamental importance to the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), but these processes have not previously been examined through fluid flow and deformation modeling. Accordingly, this modeling study will address the impact of these major processes on pore pressures and fluid flow within the prism, mega-splay fault, and plate boundary fault. The modeling will be implemented using an existing software package ABAQUS. This package offers the ability to simulate the major features important to this modeling, will allow modeling results to be reproducible by other researchers, and is flexible enough to accommodate needs of future subduction zone modeling. The model will be applied to the Kii transect of the Nankai subduction zone and used to test the following interrelated hypotheses: Hypothesis 1: The mega-splay fault system significantly alters the patterns of excess pore pressures and porosity loss within the accretionary complex. Hypothesis 2: The hydrologic role of the Nankai mega-splay system can be illuminated through observation of pore pressures, porosities, and fluid chemistry. Hypothesis 3: Underplating rejuvenates fluid expulsion at the base of the accretionary prism by transferring sediments to a different stress state and by moving the decollement zone to a less dewatered area. Although this application of the modeling is to the Kii transect of the Nankai subduction complex, an assessment of the importance of underplating and out-of-sequence thrusting for subduction zone dewatering and deformation will be useful for other subduction zones, as well as for workers in fold and thrust belts. Splay faulting and underplating are commonly inferred features that could greatly alter pore pressure and porosity distributions (and thus seismogenesis) in many subduction zones. Broader Impact Understanding seismogenic zone processes has great societal impact related to earthquake and tsunami hazards. This study will constitute an initial step in the long-term investigation of the seismogenic zone. Modeling conducted early in the investigative process can help to shape scientific strategies during drilling and monitoring. The use of the ABAQUS software package will expand the ability of the subduction zone modeling community. Model input data sets will be made available to other researchers. As an active proponent in NanTroSEIZE, Liz Screaton will directly communicate modeling results to fellow proponents and at future workshops and NanTroSEIZE-related meetings. In addition, general interest conclusions will be published in scientific journals and presented at national scientific meetings. This project will result in the training of graduate students. At University of Florida, it will be adapted to either one PhD or two M.S. students. At University of Colorado, the project work will involve a student (either MS or PhD) in the modeling. The graduate students will present at scientific meetings and the project will be a significant component of their dissertation or thesis.