RUI: Collaborative Research: Quaternary Deformation in the Cascades Foothills and Southern Puget Lowland, Washington

9627856 Umhoefer华盛顿普吉特低地位于卡斯卡迪亚辐合边缘的弧前区域，胡安达-富卡板块在这里斜向辐合在北美板块之下。相关的变形发生在俯冲板块边界或贝尼奥夫带，也发生在上（北美）板块的一个广泛而复杂的区域，横跨北加州、俄勒冈州、华盛顿州和不列颠哥伦比亚省西南部。人们提出了几种模型来解释卡斯卡迪亚边缘的第四纪变形，但目前的野外资料不足以对这些模型进行评价。该项目将研究西雅图附近活动断层上的滑动如何继续向南移动。这项工作是一个试点项目，旨在确定地表暴露和地震数据是否足以测试一个模型，该模型表明西雅图断层是整个普吉特低地下一个综合的区域逆冲系统的一部分。如果成功，研究结果将为理解这种张拉构造环境提供一个急需的模型框架，这也将为风险评估提供一个重点。

9627856 Umhoefer The Puget Lowland, Washington, is in the fore-arc region of the Cascadia convergent margin, where the Juanda Fuca plate is obliquely converging beneath the North American plate. Associated deformation occurs along the subducting plate boundary or Benioff zone and also in a wide, complex region of the upper (North American) plate extending across Northern California, Oregon, Washington and Southwestern British Columbia. Several models have been proposed to explain Quaternary deformation in the Cascadia margin, but present field data is inadequate to evaluate these models. This project will examine how slip on an active fault in the vicinity of Seattle continues to the South. The work is a pilot project to determine if surface exposures and seismic data will be adequate to test a model that suggests that the Seattle fault is part of an integrated, regional thrust system under the entire Puget-Lowland. If successful, the results will provide a much needed model framework for understanding this transtensional tectonic environment, which will also provide a focus for risk assessment.