Measuring the depth extent of processes driving the tectonic evolution of North America

自中生代以来，断裂的大陆边缘碎片、岛弧和大洋高原在北美西缘的增生促进了其生长。然而，前寒武纪年龄的上地幔下这些岩石在加拿大科迪勒拉表明，他们是由旧的岩石圈。因此，看来与北美洲这一部分的增长有关的造山作用仅限于地壳浅层。在地表和更深层次的结构之间的对比年龄代表了一个明显的偏离其他造山系统的地壳和其下地幔具有类似的演化历史的构造风格。这里提出的研究计划旨在了解岩石联合收割机形成大陆的机制，并将通过测量北美西缘的地壳和上地幔来实现这一目标。确定现今地壳和上地幔在缝合带内的结构，并将其结构与稳定的大陆区域进行比较，将澄清大陆生长的过程。该方案的短期目标是利用北美北方山脉的现有数据集，系统地绘制地壳和上地幔的结构图。 该计划还将收集新的宽带地震数据，沿着从加拿大科迪勒拉到北美内陆的剖面。新的宽频带地震数据记录的阵列位于这个急剧的横向梯度在地表变形将有助于描述岩石圈如何变化在这个结构边界的表面。整合新的和现有的地震数据集的观测结果将有助于深入了解地壳和上地幔变形部分的特性，以及这些特性与抵抗变形的区域有何不同。这些观察将解决本研究的长期目标，以确定北美西部板内变形的因素。这一长期目标将通过回答以下问题来实现：（1）重力势能和边界力的联合作用如何引起大陆内部的变形？(2)在融入大陆的过程中，非洲大陆的结构发生了哪些变化？下地壳和上地幔的哪些构造或作用影响地表构造？该计划将通过增加我们对大陆演化基本方面的理解而使地球科学界受益。此外，加拿大科迪勒拉及其周围地区的居民将受益于对可能造成区域地震灾害的地壳和上地幔结构的更好理解。

The accretion of rifted continental margin fragments, island arcs, and oceanic plateaus onto the western margin of North America has contributed to its growth since the Mesozoic. However, Precambrian ages of the upper mantle underlying these terranes in the Canadian Cordillera indicate that they are underlain by older lithosphere. It would therefore appear that the orogenic processes associated with the growth of this portion of North America were limited to the shallow crust. Contrasting ages between terranes at the surface and deeper structures represent a clear departure in tectonic style from other orogenic systems where the crust and its underlying mantle possess a similar evolutionary history. The research program proposed here seeks to understand the mechanisms by which terranes combine to form continents and will accomplish this goal by surveying the crust and upper mantle of the western margin of North America. Determining the present-day structure of the crust and upper mantle within suture zones that juxtapose formerly disparate terranes, and comparing their structures to stable continental regions, will clarify the process of continental growth. The short-term objectives of this program will be to systematically map the structure of the crust and upper mantle within and across terranes utilizing existing datasets from the northern cordillera of North America. This program will additionally collect new broadband seismic data along a profile spanning from the Canadian Cordillera into the interior of North America. New broadband seismic data recorded by arrays located at this sharp lateral gradient in surface deformation will help characterize how the lithosphere changes at this structural boundary at the surface. Integrating observations from new and already available seismic datasets will yield insights into the properties that characterize portions of the crust and upper mantle that have been deformed and how those differ from regions that resist deformation. These observations will address the long-term objective of this study to identify the factors responsible for intraplate deformation in western North America. This long-term goal will be accomplished by answering the following questions: (1) How do the combined contributions from gravitational potential energy and boundary forces cause deformation within the interior of continents? (2) In what ways do the structures of terranes change as they are integrated into continents? And (3) What structures or processes in the lower crust and upper mantle influence surface tectonics? This program will benefit the geoscience community by increasing our understanding of a fundamental aspect of continental evolution. Additionally, the population in and around the Canadian Cordillera will benefit from improved understanding of crustal and upper mantle structures that can be responsible for regional seismic hazards.