The Influence of Pre-existing Zones of Weakness on the 3D Geometry and Evolution of Extensional Faults and Folds

预先存在的薄弱带对 3D 几何形状以及伸展断层和褶皱演化的影响

• 批准号: 0838462
• 负责人: Martha Withjack
• 金额: $ 20.54万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838462&HistoricalAwards=false
• 关键词: Influence; Pre; existing; Zones; Weakness

The Earth's continental crust is heterogeneous, containing numerous pre-existing zones of weakness. How do these pre-existing zones of weakness influence the structural development of rift basins? This research project explores the hypothesis that the influence is highly variable, depending on several conditions including: 1) the attitude of the pre-existing fabric relative to the extension direction during rifting, 2) the characteristics of the pre-existing zones of weakness (i.e., their number, spacing, length), and 3) the burial depth of the pre-existing zones of weakness during rifting. To test this hypothesis, a series of scaled experimental (analog) models are run in which these three conditions vary systematically. Identical models will be conducted with dry sand and wet clay as the modeling materials to determine the sensitivity of the modeling results to the modeling medium. Additionally, the faults and fault-related folds produced in the models are compared with natural examples observed on three-dimensional seismic-reflection data from rift zones containing pre-existing zones of weakness. The integration of the results of the experimental modeling and the three-dimensional seismic analysis (data sets that yield complementary information) will provide a robust test of the hypothesis. Novel research methods include the use of thin-sections to study the details of fault interactions in clay models and the generation of three-dimensional renderings of the faults and fault-related folds produced in the experimental models using the same computer software designed for the interpretation of three-dimensional seismic-reflection data.Tectonic events have repeatedly deformed (fractured and contorted) the Earth's crust. In this project, scaled experimental models are used to study how the deformation produced during early tectonic events affects the deformation produced during subsequent tectonic events. Scaled experimental modeling is a powerful tool that has helped geoscientists understand rock deformation in three dimensions and through time. One limitation of scaled experimental modeling, however, has been the inability to observe the three-dimensional deformation in great detail. In this project, this limitation is overcome by studying the deformation in the models using thin sections (very thin slices of the model mounted on slides and viewed through a microscope) with sophisticated computer software currently used in the oil and gas industry. By combining these traditional and cutting-edge technologies, three-detailed dimensional images of the deformation within the models will be constructed, for the first time. This improved knowledge of the three-dimensional deformation patterns will have immediate applicability for earthquake prediction, ground-water flow, hydrocarbon exploration and production, and sequestration/storage of the greenhouse gas, carbon dioxide. Specifically, geoscientists will be able to use these modeling results as templates for interpreting widely spaced or poor-quality geologic or geophysical data.

地球的大陆地壳是异质的，包含许多先前存在的薄弱地带。这些先前存在的软弱地带如何影响裂谷盆地的构造发展？这项研究项目探索了这样一种假设，即影响是高度可变的，取决于几个条件，包括：1)裂谷过程中预先存在的组构相对于伸展方向的态度，2)先前存在的薄弱带的特征(即它们的数量、间距、长度)，以及3)先前存在的薄弱带在裂谷过程中的埋藏深度。为了验证这一假设，运行了一系列规模化的实验(模拟)模型，在这些模型中，这三个条件有系统地变化。以干砂和湿粘土为建模材料，进行相同的模型试验，以确定建模结果对建模介质的敏感性。此外，将模型中产生的断层和与断层相关的褶皱与从包含先前存在的薄弱带的裂谷带的三维地震反射数据观察到的自然实例进行了比较。实验建模和三维地震分析(产生补充信息的数据集)的结果的集成将提供对该假设的稳健检验。新的研究方法包括使用薄片研究粘土模型中断层相互作用的细节，以及使用为解释三维地震反射数据而设计的相同计算机软件生成实验模型中产生的断层和与断层相关的褶皱的三维效果图。构造事件一再使地壳变形(破裂和扭曲)。在这个项目中，使用缩尺实验模型来研究早期构造事件中产生的变形如何影响后续构造事件中产生的变形。比例实验模型是一个强大的工具，它帮助地球科学家了解岩石在三维和时间上的变形。然而，规模化实验模型的一个局限性是无法非常详细地观察三维变形。在这个项目中，通过使用目前石油和天然气行业中使用的复杂计算机软件研究薄片(安装在幻灯片上并通过显微镜观察的非常薄的模型切片)模型中的变形来克服这一限制。通过将这些传统技术和尖端技术相结合，将首次构建模型内变形的三维详细图像。这种对三维变形模式的改进知识将立即适用于地震预测、地下水流动、碳氢化合物勘探和生产以及温室气体二氧化碳的封存/储存。具体地说，地球科学家将能够使用这些建模结果作为模板，解释分布广泛或质量较差的地质或地球物理数据。