Extensional Deformation in Convergent Systems

对于理解收缩造山带的结构和机械演化来说，理解伸展应力产生的原因和如何在收敛边缘适应伸展应力仍然是基本的。相对较小的伸展应力可以在会聚系统的长期结构演化中发挥重要作用。这项研究主要是为了加深对伸展应力如何影响有限变形的演化、地形发育和高原形成的理解，特别是对伸展变形如何影响台湾、中央安第斯山脉和西藏等造山系中观测到的有限变形的理解。这项研究将专门讨论控制伸缩共时发生的参数，包括流变学(横向和随深度)、收敛速度和初始板块几何形状的变化，包括板块运动倾角。了解这些过程是更好地理解许多汇聚边缘的构造的基础。为此，采用了三维模拟建模和定量分析相结合的多方面建模方法，结合二维和三维有限元数值模拟和分析，旨在解决山带发展过程中几何复杂背景下的伸展和应变分配等关键地质问题。将使用能够适应重大离面变形的大型实验设备。此外，数值建模将为稳健的模拟建模方法提供一个重要的对立面，并对其进行交叉验证。这项研究为早期职业研究人员提供了一个机会，让他们了解一种鲜为人知的地震活动形变模式，同时为本科生提供研究机会，为研究生培训，并为本科生教学提供研究成果的增强。

Understanding why extensional stress occurs and how it is accommodated at convergent margins remains fundamental to understanding the structural and mechanical evolution of contractional orogens. A relatively small amount of extensional stress can play an important role in the long-term structural evolution of convergent systems. This study is broadly focused on improving the understanding of how extensional stress can affect the evolution of the finite deformation and the development of topography and the formation of plateaus and, specifically, towards understanding how extensional deformation has influenced the finite deformation observed in orogenic systems such as Taiwan, the Central Andes, and Tibet. This study will specifically address the parameters that control the occurrence of extension coeval with contraction, including variations in rheology (laterally and with depth), convergence rate, and initial plate geometries, including plate motion obliquity. Understanding these processes is fundamental to a better understanding of the tectonics of many convergent margins. To this end, a multifaceted modeling approach is being used that employs three-dimensional analog modeling with quantitative analysis in conjunction with two and three-dimensional finite element numerical modeling and analytical analysis.The experiments in this study are designed to address key geological issues of extension and strain partitioning in geometric complex settings during the development of mountain-belts. A large experimental apparatus that can accommodate significant out-of-plane deformation will be used. Additionally, numerical modeling will provide an essential counterpoint to, and a cross-check for, the robust analog modeling method. The study provides an opportunity for early career investigators to learn about a poorly understood mode of seismically active deformation while providing research opportunities for undergraduate students, graduate student training, and research derived enhancements to undergraduate teaching.