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

该项目将调查日本四万十带与俯冲有关的断层岩，以评估二氧化硅重新分布在俯冲带断层岩愈合中的作用。这些断层岩记录了在跨越孕震区的温度和深度发生的变形（即，大多数地震的起源地）。我们假设，二氧化硅的再分布是一个可行的过程，故障愈合的时间尺度相关的地震（地震）周期，因此可以显着影响的位置，频率和地震事件，如破坏性的2011年东北冲地震的震级。了解这些愈合过程对地震预测和地震灾害具有潜在的意义。高知大学的Yoshitaka Hashimoto博士将作为我的领域知识的来源，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地球化学过程的作用，这些过程有助于愈合与俯冲有关的断层岩。从代表孕震区的多个混杂岩中提取四万十带的相关断层组构和矿脉，以评估二氧化硅再分布在愈合断层岩中的作用。拟议的研究包括（1）野外工作，收集样品进行分析和收集结构测量（2）使用表征技术（即，EPMA、FE-SEM）研究二氧化硅的溶解和沉淀过程;（3）岩石学表征脉和剪切组构的分布和尺寸（即间距和厚度）。来自拟议研究的数据将有助于更好地约束二氧化硅重新分布的动力学模型，该模型将评估俯冲带愈合的时间尺度。评估断层愈合沿着俯冲界面的时间尺度将使我们能够研究愈合过程与俯冲带地震周期之间的联系。该奖项是东亚和太平洋夏季研究所计划下的一项奖励，由NSF和日本科学促进会共同资助，资助一名美国研究生的夏季研究。

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.