Collaborative Research: Multiscale Travel Time Tomography of the Mantle to 1000 km Depth Beneath the Western USA

记录在美国西部的远震数据提供了关于北美地幔结构性质的信息，北美地幔是地球内部的一部分，是由海洋岩石圈俯冲的复杂历史形成的。断层摄影成像通常归因于俯冲板块的高速构造，但并不像我们目前对俯冲地质历史的理解所期望的那样简单。因此，这些图像提供了有关实际俯冲历史、年轻俯冲板块的命运以及上地幔和跨过渡带到下地幔的对流流动的关键信息。受拉拉米造山运动影响的地区现在正在经历美国西部大部分地区的小规模对流，假定的黄石火山羽流（可能）正在与俯冲的板块和小规模的下沉流相互作用。了解这种丰富的地质过程，并从彼此中分离出单个结构，需要仔细和准确的地震成像。该项目的目标是通过创建一个从地壳底部延伸到约1000公里深度的全面的三维纵波速度模型，来测试关于美国西部复杂历史的特定假设。地震建模将结合所有可用的本地、区域和全球旅行时数据集，以及最新的地壳和过渡带结构约束。此外，它还使用有限频率技术（在有用的地方）和3-D波传播技术。这项工作养活了两个研究生。

Teleseismic data recorded across the western U.S. provide information on the structural nature of the mantle beneath North America, a volume of Earth's interior that has been shaped by a complex history of subduction of oceanic lithosphere. Tomography images high-velocity structures that are commonly attributed to subducted slabs but which are not as simple as expected from our current understanding of the geologic history of subduction. Hence, such images hold key information on the actual subduction history, the fate of young subducted slabs, and convective flow in the upper mantle and across the transition zone to the lower mantle. The area affected by the Laramide orogeny is now experiencing small-scale convection beneath most of the western U.S., and a presumed Yellowstone plume is (probably) interacting with subducted slab and small-scale downwellings. Understanding this richness of geological processes and resolving the individual structures from one another requires careful and accurate seismic imaging. The goal of this project is to test specific hypotheses about the complex history of the western U.S. by creating a comprehensive 3-D P-wave velocity model extending from the base of the crust to ~1000 km depth. The seismic modeling will combine all available local, regional, and global travel-time datasets with newly available constraints on crust and transition zone structure. In addition, it uses finite frequency techniques (where useful) and 3-D wave propagation techniques. This work supports two graduate students.