What Locks Subduction Thrusts?

根据这份合同，该项目将研究一个有充分记录的始新世-古新世岩石复体，该复体来自于一个现暴露于阿拉斯加的古俯冲逆冲，目的是量化和理解俯冲信托的上部地震部分与下部地震部分在各种长度尺度上的差异。这项研究将检验这样一种假设，即在两次大地震之间，裂缝中的矿物沉积加强并锁住了俯冲逆冲。在野外工作中，PI和一名博士生将记录不同世代的结构结构和矿脉的变化。随后的实验室研究将着眼于在类似的PT条件下的物理性质和矿物学变化，就像目前在日本西南俯冲带存在的那样。剪切带参数的量化、矿物学变化、压力溶液强度、密度和孔隙度、块体和基质的大小/形状，将有助于解释简单滑动（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表明滑动、粘滑和加热的纹理和结构特征。这些观测和测量，包括与Vrolijk进行的流体包裹体研究，将有助于测试实际俯冲带中速度减弱的想法，为实验人员提供关于哪种类型的材料最适合变形研究的指导，为南开隔管钻探提供预览，以及为解释俯冲复合体中10-100米尺度的三维地震研究提供约束。

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.