Rheology and earthquakes in subduction zones

该项目的主要目的是将现场和实验室的断层研究、确定断层带流变和运输特性的实验研究以及断层运动的理论/数值分析结合起来，以便更好地了解俯冲带地震的机制。本研究的补助金是用来安装伺服控制的致动器轴向加载和围压到我们的容器内变形流体流动装置和修改低速到高速水热摩擦装置，以稳定在孔隙水压力下的高速实验围水压力和轴向载荷。血管内仪器的扩展使得完成一个非常易于使用的渗透率/孔隙度测量系统成为可能。通过对低速-高速装置的改进，在世界上首次实现了在孔隙水压力作用下，以高达数米的速度再现断层运动的地震记录 ...更多信息 每秒这两个系统将在未来几年内提供大量关于断层带特性的独特数据。主要科学成果如下。（1）热加压过程，即，根据实测的中线构造带和哈那热断层的渗透率结构，分析了摩擦热引起的孔隙压力上升。这种机制被证明是产生滑动弱化距离的断层，Dc，相同的顺序，地震确定的值，为第一次。传统的实验室资料显示Dc比地震值小几个数量级，因此我们的工作实质上填补了断层研究与地震学之间的差距。（2）对摩擦熔融过程进行了详细的研究，证明摩擦熔融过程的影响可以通过求解Stefan问题来评价，摩擦熔融可以作为深部断层运动的润滑剂，摩擦熔融过程也产生了与地震测定级接近的Dc（3篇论文）。（3）利用马里亚纳海沟后哈哈岛蛇纹海山中的蛇纹岩进行了摩擦实验，结果表明，大规模逆冲型地震可能受到蛇纹化楔地幔低温蛇纹岩的抑制。(4)使用孕震区底部附近的真实断层特性模拟板块边界运动，重现了最近在俯冲带中发现的缓慢滑动事件。少

The main purpose of this project has been to integrate fault studies in the field and laboratory, experimental studies to determine rheological and transport properties of fault zone and theoretical/numerical analyses of fault motion towards better understanding of mechanisms of subduction-zone earthquakes. The present research grant-in-aid was used to install servo-controlled actuators for axial loading and confining pressure onto our intravessel deformation-fluid-flow apparatus and to modify low-to-high velocity hydrothermal friction apparatus to stabilize confining water-pressure and axial load during high-velocity experiments under pore-water pressure. The extension of intravessel machine has made it possible to complete a-very-easy-to-use system for permeability/porosity measurements. The modification of low-to-high velocity apparatus has made it possible, for the first time in the world, to reproduce seismic fault motion with pore-water pressure at velocities up to several meters … More per second. The two systems will provide numerous unique data on fault-zone properties for years to come. The main scientific outcomes are as follows. (1)Thermal pressurization process, i.e., pore pressure rise due to frictional heating, was analyzed based on measured permeability structures of Median Tectonic Line and Hanaore fault (two papers). This mechanism was shown to yield slip-weakening distance of fault, Dc, of the same order as that of seismically determined values, for the first time. Traditional laboratory data showed Dc smaller that seismic values by a few orders of magnitude, so that our work has filled the gap between fault studies and seismology substantially. (2)Frictional melting processes have been studied in very detail and we showed that the effect of frictional melting processes can be evaluated by solving a Stefan problem, that frictional melt can act as lubricant to fault motion at depths, and that frictional melting processes also yield Dc close to seismically determined order (3 papers). (3)Friction experiments have been conducted using serpentinite recovered from Haha-jima serpentine seamount behind Mariana trench and our results suggests a possibility that great thrust-type earthquakes are suppressed by low-temperature serpentine of serpentinized wedge mantle. (4) Simulation of plate boundary motion using realistic fault properties near the base of seismogenic zone reproduced slow slip events recently recognized in subduction zones. Less