What Locks Subduction Thrusts?

根据这一奖项，PI将研究记录充分的始新世-古新世岩石复合体，来自一次古俯冲推覆，现在暴露在阿拉斯加，以便在不同的长度尺度上量化和了解俯冲托拉斯的上部无地震部分和下部孕震部分之间的差异。这项研究将检验这一假设，即在两次大地震之间，裂缝中的矿物沉积加强并锁定了俯冲推覆。在野外工作中，PI和一名博士生将记录不同世代的结构组构和矿脉的变化。稍后的实验室研究将观察类似于日本西南部俯冲带目前存在的PT条件下物理性质和矿物学的变化。剪切带参数的量化、矿物学的变化、压力溶液的强度、密度和孔隙度以及块体和基质的大小/形状，将允许解释简单滑动(无地震)与粘滑(地震)行为的重要性。此外，实验室实验的结果可以用来解释指示滑动、粘滑和加热的纹理和结构特征。这些观测和测量，包括用Vrolijk进行的流体包裹体研究，将有助于检验有关实际俯冲带速度减弱的想法，为实验者提供指导，说明哪些类型的材料最适合进行变形研究，预览南开立管钻井将看到的情况，以及在俯冲复合体中解释三维地震研究的10-100米尺度约束。

Under this award, the PI will examine a well-documented Eocene- Paleocene rock complex from a paleo subduction thrust, now exposed in Alaska, in order to quantify and understand the differences, at a variety of length scales, between the upper aseismic parts of a subduction trust and the lower seismogenic parts. This study will test the hypothesis that deposition of minerals in cracks strengthens and locks subduction thrusts in the periods between major eatthquakes. During field work, the PI and a PhD student will document changes in structural fabric and mineral veins of various generations. Later lab studies will look at changes in physical properties, and mineralogy under similar PT conditions as presently exist in the SW Japan subduction zone. Quantification of shear zone paramenters, changes in mineralogy, intensity of pressure solution, density and porosity, and size/shape of blocks and matrix, will allow interpretations of the importance of simple sliding (aseismic) vs. stick-slip (seismic) behavior. Further, the results of the lab experiments can be used to interpret textures and structural features indicative of sliding, stick-slip, and heating. These observations and measurements, including fluid inclusion studies with Vrolijk, will be useful for testing ideas about velocity weakening in actural subduction zones, providing guidance for experimentalists on what types of materials are best for deformation studies, a preview of what will be seen in riser drilling at Nankai, and 10-100m scale constraints on interpreting 3D seismic studies in subduction complexes.