SGER AWARD: A Potential Example of Fold Growth Due to Kink-Band Migration on Near Earthquake-Cycle Timescales

SGER 奖：近地震周期时间尺度上扭结带迁移引起的褶皱增长的潜在例子

• 批准号: 0232603
• 负责人: Andrew Meigs
• 金额: $ 1.89万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0232603&HistoricalAwards=false
• 关键词: SGER; AWARD; Potential; Example; Fold

One of the most active debates in structural geology over the last 20 years has focusedon the existence of folds formed due to kink-band migration (e.g. the fault-bend (FBF) andfault-propagation (FPF) folds).A suite of folded geomorphic surfaces in western Argentinahave been identified that apparently display the essential geometrical characteristics of foldingdue to kink-band migration. Because the folded surfaces are closely associated with flexuralslip surface faulting in an earthquake in 1944,this site may contain the first evidence of kink-band migration on near earthquake cycle time scales. The primary purpose of this exploratoryresearch is to establish whether the structural geometry of a suite of folded geomorphicsurfaces is consistent with fundamental predictions of kink-band migration fold growth. Thepresent knowledge of their structural characteristics is limited, however, which precludes cleardefinition of their potential for providing new insight into kink-band migration and foldingmechanisms in general. Thus, an exploratory grant is sought to develop an initial data set fromthese unique, superbly exposed surfaces to define more clearly the potential and direction forfuture investigation. Key objectives of this initial investigation include:(1)understanding thegeometrical evolution of folds at the spatial and temporal scale of successively youngergeomorphic surfaces;(2)detailed characterization of the geomorphology of the surface of anactively growing emergent fold in which fold growth and erosion/deposition are out-of-phase;and (3)determination of the extent to which kink-band migration folding is the mechanism bywhich this fold is growing. These data and analyses will help to frame more explicitlyquestions regarding the structural and geomorphic evolution of this and other growing folds inthe region, the interplay between fold growth and intervening periods of erosion anddeposition, and the incremental growth of folds at near-earthquake time scales. Increased knowledge of fold growth on this time scale has potential impacts for understanding the earthquake hazard associated with active blind faults, the interpretation of fold growth history from syntectonic strata, petroleum exploration in basins characterized by syntectonic sedimentation and in regions of basement-involved thrusting, and fault-related fold models.

近20年来，构造地质学中最活跃的争论之一集中在扭扭带迁移形成的褶皱的存在上，例如断层弯曲褶皱（FBF）和断层传播褶皱（FPF）。在阿根廷西部发现了一组褶皱地貌表面，这些表面由于扭结带迁移而明显地表现出褶皱的基本几何特征。由于褶皱面与1944年地震中的弯曲滑动面断裂密切相关，该地点可能包含在近地震周期时间尺度上扭结带迁移的第一个证据。本探索性研究的主要目的是确定一组褶皱地貌表面的结构几何形状是否与扭结带迁移褶皱生长的基本预测相一致。然而，目前对其结构特征的了解是有限的，这妨碍了对扭结带迁移和一般折叠机制提供新见解的潜力的明确定义。因此，探索性资助旨在从这些独特的、高度暴露的表面开发初始数据集，以更清楚地定义未来研究的潜力和方向。本初步研究的主要目标包括：(1)在连续年轻地貌表面的时空尺度上了解褶皱的几何演化；(2)详细描述了逆生长急出褶皱表面的地貌特征，其中褶皱的生长与侵蚀/沉积是相异的；(3)确定扭结带迁移褶皱在多大程度上是该褶皱生长的机制。这些数据和分析将有助于更明确地提出有关该地区其他生长褶皱的结构和地貌演化的问题，褶皱生长与侵蚀和沉积之间的相互作用，以及近地震时间尺度上褶皱的增量生长。在这一时间尺度上增加对褶皱生长的认识，对于理解与活动盲断裂相关的地震危险性、从同构造地层解释褶皱生长历史、在以同构造沉积为特征的盆地和基底相关逆冲地区进行石油勘探以及与断层相关的褶皱模型具有潜在的影响。