EAPSI: The Role of Silica-redistribution in Healing Subduction-related Fault Rocks

该项目将调查日本岛本带与俯冲有关的断层岩，以评估二氧化硅再分布在俯冲带断裂岩愈合中的作用。这些断层岩记录了在跨越地震孕育区(即大多数地震的发源地)的温度和深度下发生的变形。我们假设，二氧化硅重新分布是在与地震(地震)周期相关的时间尺度上修复断层的可行过程，因此可以显著影响地震事件的位置、频率和震级，例如2011年破坏性的东北-冲之地震。了解这些愈合过程对地震预测和地震风险具有潜在的意义。高知大学的Yoshitaka Hashimoto博士将作为我的野外领域的知识来源，并将提供表征设备，使我能够进一步了解二氧化硅重新分布和其他有助于修复与俯冲相关的断层岩石的地球化学过程的作用。该项目将从代表地震孕育带的多个混杂岩带研究与俯冲相关的断层组构和矿脉，以评估二氧化硅重新分配在修复断层岩石中的作用。拟议的研究包括(1)现场工作以收集样品进行分析和收集结构测量(2)利用表征技术(即EPMA、FE-SEM)对矿脉和滑面(即鳞片状组构)进行地球化学分析，以研究二氧化硅的溶解和沉淀过程；(3)从岩石学角度表征矿脉和剪切组构的分布和尺寸(即间距和厚度)。这项拟议研究的数据将有助于更好地约束二氧化硅再分布的动力学模型，该模型将评估俯冲带愈合的时间尺度。评估俯冲界面上断层愈合的时间尺度将使我们能够调查俯冲带中断层愈合过程和地震周期之间的联系。该奖项由东亚和太平洋夏季研究所计划设立，支持一名美国研究生的夏季研究，由NSF和日本科学促进会共同资助。

This project will investigate subduction-related fault rocks in the Shimanto Belt of Japan in order to assess the role of silica redistribution in the healing of subduction zone fault rocks. These fault rocks record deformation that occurred at temperatures and depths that span the seismogenic zone (i.e., where most earthquakes originate). We hypothesize that silica redistribution is a viable process for fault healing on timescales relevant to earthquake (seismic) cycles and therefore can significantly impact the location, frequency, and magnitude of seismic events such as the destructive 2011 Tohoku-Oki earthquake. Understanding these healing processes has potential implications for seismic prediction and seismic hazard. Dr. Yoshitaka Hashimoto of Kochi University will serve as source of knowledge for my field areas and will also provide characterization equipment that will allow me to further our understanding of the role of silica redistribution and other geochemical processes that contribute to healing subduction-related fault rocks.This project will study subduction-related fault fabrics and veins in the Shimanto Belt from multiple mélanges that represent the seismogenic zone in order to assess the role of silica redistribution in healing fault rocks. The proposed research includes (1) field work to gather samples for analyses and to collect structural measurements (2) geochemical analyses of veins and slip surfaces (i.e. scaly fabrics) using characterization techniques (i.e., EPMA, FE-SEM) to investigate processes of dissolution and precipitation of silica and (3) petrographically characterizing the distribution and dimensions of veins and shear fabrics (i.e. spacing and thickness). The data from the proposed research will help to better constrain a kinetics model for silica redistribution that will assess timescales of subduction zone healing. Evaluating the timescales of fault healing along the subduction interface will allow us to investigate the connection between healing processes and the seismic cycle in subduction zones.This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.