EAPSI: Using 3D numerical models to understand deformation of an active salt system in Needles District, Utah

犹他州东部的景观，包括摩押谷、拱门和蒙纳兰国家公园，都受到地下盐存款的流动和溶解的影响。这些沉积物是地球上最脆弱的岩石之一，在浅深度处塑性流动，变形，破裂和移动覆盖在沉积岩上的岩石。针区位于犹他州南卡罗来纳州国家公园，由于盐流入科罗拉多河切割的大峡谷，针区正在积极变形。为了研究盐的流动、上覆岩石的破坏以及通过科罗拉多河的流体输送，将制作三维数值模型。本研究的重点是了解断层如何发展和相互作用，以及盐的塑性流动如何与脆性上覆沉积地层耦合。这项研究将在新西兰惠灵顿的GNS进行，允许使用强大的建模软件和地形建模师Phaedra厄普顿博士的专业知识。针区暴露了一系列积极蠕动的正断层，这些正断层在蒸发岩沉积物的塑性变形基底上方容纳重力驱动的延伸。这项研究将使用Flac3D创建三维力学模型，以了解针区活动变形背后的力学。模型将说明1）沉积单元中预先存在的弱点（即接头）如何控制断层表达，2）盐层中的异质性如何影响变形模式，以及3）变化的盐流和溶解速率如何影响系统。这些模型将产生盐如何变形的数学和可视化的解决方案，它是耦合到覆盖层的脆性破坏。模拟塑性流动和脆性变形如何耦合以及盐作为盐的非均匀性，可以创建一个更精确的岩石力学图片，还有待探索，并可能被应用到其他地区的伸展构造环境。这个NSF EAPSI奖是与新西兰皇家学会合作资助的。

The landscape of eastern Utah, including Moab Valley, Arches, and Canyonlands National Parks, is influenced by flow and dissolution of a buried salt deposit. These deposits are some of the weakest rocks on Earth and flow plastically at shallow depths, deforming, breaking, and moving overlying sedimentary rock. The Needles District, located in southern Canyonlands National Park, Utah, is actively deforming due to salt flow into the large canyon incised by the Colorado River. To investigate how salt flow, failure of the overlying rock, and fluid transport through the Colorado River, three-dimensional numerical models will be produced. The focus of this study is to understand how faults develop and interact and how plastic flow of the salt is coupled to the brittle overlying sedimentary formations. This research will take place at GNS, Wellington, New Zealand, allowing access to a powerful modeling software and the expertise of landform modeler, Dr. Phaedra Upton. The Needles District exposes an array of actively creeping normal faults that accommodate gravity-driven extension above a plastically deforming substrate of evaporite deposits. This research will create three-dimensional mechanical models using Flac3D to understand the mechanics behind active deformation in the Needles District. Models will address how 1) preexisting weaknesses (i.e. joints) in the sedimentary units control fault expression, 2) heterogeneity in the salt layer affects deformation patterns, and 3) varying salt flow and dissolution rates influence the system. These models will yield mathematical and visual solutions of how salt deforms and it is coupled to brittle failure of the overburden. Modeling how plastic flow and brittle deformation are coupled as well as salt heterogeneity can create a more precise picture of rock mechanics that has yet to be explored and can potentially be applied to extensional tectonic settings in other regions. This NSF EAPSI award is funded in collaboration with the Royal Society of New Zealand.