Three-Dimensional Characterization of a Pseudotachylyte-Bearing Fault

断层滑动是地球上地壳变形的主要方式。 然而，地壳内的断层表现出一系列的行为，从地震产生的粘滑到地震蠕变。 由地震学推导出的摩擦定律可以解释断层行为的这一频谱;然而，将这些定律与自然地震的条件进行换算以及解释定律的物理意义已被证明是一个艰巨的挑战。 这项研究将桥梁实验室和地震规模的三维几何成像的假玄武玻璃轴承故障。 假玄武玻璃是由摩擦熔融形成的断层岩，通常被认为是地震滑动速度保存在断层带中的唯一明确证据。 摩擦熔体的固化“冻结”震源几何形状，但是，它也排除了广泛的断层表面暴露，使以前的研究断层带几何形状的发展。 我们已经克服了这个困难，通过成像的完整的三维几何形状的故障，使用高分辨率的X射线计算机断层扫描（CT）。 在这项研究中，我们将使用自然和实验断层表面的CT图像，以量化表面粗糙度，摩擦接触面积和pseudotachylyte厚度，从而确定断层粗糙度的演变与滑动和估计关键的摩擦参数在地震成核和传播尺度。 拟议的项目将提高对地震及其影响的认识，这是国家减少地震灾害计划的主要目标之一。 此外，该项目还将在美国主要的本科院校卫斯理大学与意大利世界知名研究机构国家地球物理和火山学研究所（INGV）的科学家之间建立新的合作关系。 本科生将在该项目中发挥不可或缺的作用，为未来的国际和跨学科研究埋下种子，研究地壳的脆性变形过程。 这些学生将体验科学过程的全部范围，从假设生成，到研究设计，再到在专业会议和书面论文中展示结果。该项目得到了国际科学和工程办公室全球风险基金的支持。

Fault slip is the dominant mode of deformation in the earth's upper crust. Faults within the crust, however, exhibit a range of behavior, from earthquake-generating stick-slip to aseismic creep. Laboratory-derived friction laws can explain this spectrum of fault behavior; however, the scaling of these laws to the conditions of natural earthquakes and the interpretation of the laws' physical meanings have proven to be formidable challenges. This research will bridge laboratory and earthquake scales by imaging the three dimensional geometry of pseudotachylyte-bearing faults. Pseudotachylytes, fault rocks formed from frictional melts, are generally considered the only unequivocal evidence ofearthquake slip velocities preserved in fault zones. The solidification of frictional melt "freezes in" earthquake source geometries; however, it also precludes the development of extensive fault surface exposures that have enabled previous studies of fault zone geometry. We have overcome this difficulty by imaging the intact 3D geometry of the fault using high-resolution X-ray computed tomography (CT). In this study we will use CT imagery of natural and experimental fault surfaces to quantify surface roughness, frictional contact area, and pseudotachylyte thickness and will thus determine the evolution of fault roughness with slip and estimate key frictional parameters at earthquake nucleation and propagation scales. The proposed project will improve the understanding of earthquakes and their effects, one of the primary goals of the National Earthquake Hazard Reduction Program. Furthermore, the project will establish a new collaboration between Wesleyan University, a primarily undergraduate institution in the US, and scientists from the Istituto Nazionale di Geofisica e Vulcanologia (INGV), a world-renowned research institute in Italy. Undergraduate students will play an integral role in the project, planting the seeds for future international and interdisciplinary research into the processes of brittle deformation in the earth's crust. These students will experience the full scope of the scientific process, from hypothesis generation, to study design, to presentation of results at professional meetings and in a written thesis. The project is being supported by the EAR Tectonics Program and the Office of International Science and Engineering's Global Venture Fund.