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.
