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

自中生代以来，裂谷大陆边缘碎片、岛弧和海洋高原在北美西部边缘的增生促进了它的发展。然而，加拿大科迪勒拉地区这些地体下面的上地幔的前寒武纪时代表明，它们下面是更古老的岩石圈。因此，与北美这部分地区的生长有关的造山作用似乎仅限于浅层地壳。地表地体和深层构造年龄的对比表明，在构造风格上与其他造山带系统明显不同，在造山带系统中，地壳及其下伏的地幔具有相似的演化历史。这里提出的研究计划旨在了解地体结合形成大陆的机制，并将通过测量北美西部边缘的地壳和上地幔来实现这一目标。确定缝合带内地壳和上地幔的现今结构，并将它们的结构与稳定的大陆区域进行比较，将澄清大陆生长的过程。该项目的短期目标是利用北美北部科迪勒拉的现有数据集，系统地绘制地壳和上地幔的结构。******该项目还将沿着从加拿大科迪勒拉到北美内部的剖面收集新的宽带地震数据。新的宽带地震数据记录的阵列位于这个表面变形的急剧横向梯度将有助于描述岩石圈如何在这个构造边界的表面变化。整合来自新的和已经可用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征，以及它们与未变形区域的区别。这些观察结果将解决本研究的长期目标，即确定导致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共同作用如何引起大陆内部的变形？(2)当地体与大陆结合时，它们的结构发生了怎样的变化？(3)下地壳和上地幔的哪些结构或过程影响地表构造？这个项目将通过增加我们对大陆演化的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地壳和上地幔结构的进一步了解，这些结构可能是造成区域地震危险的原因。

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.