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

美国西部记录的远震数据提供了有关北美地幔结构性质的信息，北美地幔的体积是由海洋岩石圈俯冲的复杂历史塑造的。层析成像成像的高速构造通常被归因于俯冲板块，但从我们目前对俯冲地质历史的理解来看，这些构造并不像预期的那么简单。因此，这样的图像包含了有关实际俯冲历史、年轻俯冲板块的命运以及上地幔中的对流和穿过过渡带到下地幔的对流的关键信息。受拉拉米德造山运动影响的地区目前正在美国西部大部分地区下方经历小规模对流，推测的黄石热柱(可能)正在与俯冲板块和小规模下沉相互作用。了解这种丰富的地质过程，并将各个构造相互区分开来，需要仔细而准确的地震成像。该项目的目标是通过建立一个从地壳底部延伸到约1000公里深度的综合三维P波速度模型来检验关于美国西部复杂历史的具体假设。地震模拟将把所有可用的局部、区域和全球旅行时数据集与最新可用的地壳和过渡带结构约束结合在一起。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。这项工作资助了两名研究生。

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.