CAREER: Very Broadband Rheology and the Internal Dynamics of Plate Boundaries on Earth

板块边界是集中热流和强烈地震活动的中心。板块边界动力学中的一个关键问题是理解变形是如何在内部组织起来产生宏观强度、结构和热质传输效率的。为了从观测的角度解决这些问题，我们需要从地震波场中提取尽可能多的关于粘性结构的信息。该项目的核心是一种方法，用于计算与地球物理学相关的广泛时间尺度上的流变特性，从地震波频率到与板块构造相关的应变率，这里称为“甚宽带流变学”。 在开发该方法的同时，我与地震学家、岩石学家、大地测量学家和地球动力学家合作，以比较的方法将其应用于一系列（原始）板块边界环境（例如东非裂谷和科罗拉多高原/盆地山脉省的边缘&）。（包括状态，成分和结构变量），我们计算弹性，滞弹性和粘性性质。然而，对这一问题的所有方面，无论是在地震学（反演地震波场以确定地球中的速度和衰减分布的方法）还是在矿物/岩石物理学（确定整个时间尺度范围内的力学性质的微观和中尺度过程）方面，都存在着大量不完全的理解。构建这种方法将阐明什么是未知的，什么是重要的，以及我们的解决方案和解释对每个不确定性来源的敏感程度。例如，我们可以评估热结构中的不确定性与水和熔体对粘度、衰减和弹性的影响中的不确定性相比的相对严重性。这种映射的灵活和开源方法将使社区能够评估我们集体理解中的漏洞和限制。该项目的教育部分包括编制关于这一方法的观察、理论和实验背景的研究生课程。

Plate boundaries are the locus of both focused heat flow and intense seismic activity. A critical problem in the dynamics of plate boundaries is to understand how deformation organizes internally to produce the macroscopic strength, structure and efficiency of heat and mass transport. To address these questions from an observational perspective, we need to extract as much information as possible from the seismic wave field about the viscosity structure. The core of this project is a methodology for calculating rheological properties across the broad spectrum of time scales relevant to geophysics, from seismic wave frequencies to strain rates associated with plate tectonics, referred to here as "Very Broadband Rheology". While developing the methodology, I am applying it to a range of (proto-) plate boundary settings in a comparative approach (e.g. East African Rift and the margins of the Colorado Plateau/Basin & Range provinces), in collaboration with seismologists, petrologists, geodesists and geodynamicists.For a given set of thermodynamic variables (including state, compositional and structural variables), we calculate the elastic, anelastic and viscous properties. However, there is a great deal of incomplete understanding in all aspects of this problem, both in seismology (in the methodology of inversion of the seismic wave field for velocity and attenuation distribution in the Earth) and in mineral/rock physics (in the processes at the micro- and meso-scales that determine the mechanical properties across the spectrum of time scales). Constructing this methodology will illuminate what is not known and also what is important to know, and how sensitive our solutions and interpretations will be to each source of uncertainty. We can assess, for example, the relative severity of the uncertainties in the thermal structure compared to uncertainty in the effects of water and melt on viscosity, attenuation and elasticity. A flexible and open source methodology for this mapping will enable the community to assess the holes and limitations in our collective understanding. The educational components of this project include the development of a graduate-level course on the observational, theoretical and experimental background for this methodology.