CAREER: Faults, fluids, friction, and fracture mechanics

是什么决定了断层的摩擦强度？断层滑动在空间和时间上是如何分布的？长期以来，人们一直把重点放在快速积累的滑动和应力释放，从地震产生的动态断裂与地震间隔期间被视为一个相对平静，然而，最近的观察和迹象缓慢，asesterian滑动提出了根本性的问题，在整个地震周期的运作故障。在主要断层之间，有多大比例的相对运动是以这种缓慢滑动的方式发生的？它是如何适应应力沿着断层的释放和传递的？是什么使这种稳定但加速的滑动速率及其迁移成为可能？从观测中可以推断出什么关于作用力、断层或整体流变学的信息？在最近的工作中，研究人员已经提出了一个定量的理解，如何缓慢的断层滑动可能会启动和传播作为一个响应不同的强迫条件。我们发现存在的分析解决方案缓慢，稳定的断层滑动响应的主要驱动因素，如突然步骤的应力断层，区域自由容纳断层滑动率升高，和流体来源。新的分析方法提供了几种途径，以确定故障操作的基础上，远程和本地的观察。这些数据包括最近的现场钻孔实验监测流体注入和地震断层位移，以及大地测量和地震学推断的慢滑迁移和时刻释放率。这些观测结果将直接与上述类型的解进行比较，以确定断层摩擦、弹性和强迫条件的耦合是否足以解释观测到的行为;如果是，则对摩擦参数、滑移的时空演化和驱动因素的一阶特征进行推断。分析解决方案的进一步开发以及与实地观测的比较将受益于与MINES ParisTech和Université Nice Sophia Antipolis教师的国际合作。为了解决一个共同的问题，即识别由机制相互作用产生的简单但基本的缩放，PI将开发一系列实验演示，以激发初中和高中学生对STEM的兴趣。开发将与塔夫茨大学的本科生合作完成，他们将通过课堂实验吸引初中和高中学生。这些实验将作为定量观察现象的演示和练习，允许与理论模型进行比较。这些演示随后将适用于本科课程。

What determines the frictional strength of a fault and how is fault slip distributed in space and time? The focus has long been on the rapid accumulation of slip and stress release from earthquake-generating dynamic ruptures with the interseismic period being seen as one of relative quiescence; however, recent observations of and indications for slow, aseismic slip has raised fundamental questions on the operation of faults throughout the seismic cycle. What proportion of relative motion across major faults occurs as such slow slip; how does it accommodate the release and transfer of stress along a fault; what permits this stable, yet accelerated, rate of slip and its migration; and what may be inferred about the forcing or about the fault or bulk rheology from observations?In recent work, the researcher has advanced a quantitative understanding of how slow fault slip may be initiated and propagated as a response to different forcing conditions. We find the existence of analytical solutions for slow, stable fault slip in response to principal driving factors such as sudden steps of stress on a fault, regions freely accommodating elevated rates of fault slip, and fluid sources. The novel analytical approach provides several avenues to identify fault operation on the basis of remote and local observations. These include data from recent field borehole experiments monitoring fluid injection and aseismic fault displacement, as well as geodetic and seismological inference of slow slip migration and moment release rates. Such observations will be directly compared with solutions of the type described above to determine whether the coupling of fault friction, elasticity, and a forcing condition is sufficient to account for observed behavior; and, if so, the inference of frictional parameters, spatiotemporal evolution of slip, and first-order characteristics of the driving factors. Further development of the analytical solutions and comparison with field observations will benefit from international collaborations with faculty at MINES ParisTech and Université Nice Sophia Antipolis. Appealing to a common problem of identifying simple, yet fundamental, scalings arising from the interplay of mechanisms, the PI will develop a series of experimental demonstrations to excite STEM interest in middle and high school students. The development will be done in collaboration with undergraduate students at Tufts University, who will in turn engage middle and high school students through in-class experiments. The experiments will serve as both demonstrations and exercises in quantitative observation of phenomena, permitting comparisons with theoretical models. The demonstrations will subsequently be adapted for undergraduate courses.