Using 230Th/U Dating of Pedogenic Carbonate to Provide a Time-Axis for Slip on the Elsinore Fault, Southern California

利用成土碳酸盐的 230Th/U 测年为南加州埃尔西诺断层上的滑动提供时间轴

• 批准号: 0636053
• 负责人: Warren Sharp
• 金额: $ 12.17万
• 依托单位: Berkeley Geochronology Center
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0636053&HistoricalAwards=false
• 关键词: Using; 230Th; Dating; Pedogenic; Carbonate

Continental plate boundaries commonly consist of broad regions of deformation characterized by fault systems consisting of multiple, approximately parallel faults, such as the San Andreas fault system of California. To better quantify the seismic hazard posed by such faults, it is essential to determine their pattern of motion through time. While recent advances in geodetic observations in the vicinity of plate boundary fault systems provide unprecedented insight into patterns of crustal deformation on the relatively short (i.e., decadal) timescale, it is likely that over longer timescales seismogenic faults exhibit variable displacement rates. That is, slip rates derived from geodetic data may reflect transient motions associated with large earthquakes in the recent past, or other recent changes in crustal loading. On a longer timescale, slip rates on major faults such as the San Andreas of southern California are thought to have varied by about a factor of two within the last approximately100,000 years. Such variability, if confirmed, could perhaps result from redistribution of slip due to evolving crustal structural complexities, clustering of earthquakes on intermediate timescales (i.e., approximately 10,000 years), or other mechanisms. Quantifying fault slip rates on timescales of 1 to 100,000 years is therefore fundamental to an improved understanding of continental dynamics and will serve societal needs for improved quantification of seismic hazards near major fault systems. Reliable measurements of fault slip on the timescale of 1 to 100,000 years, however, are quite limited in number. This is in part because of the relative rarity of geological situations that preserve the appropriate stratigraphic or geomorphologic information needed to precisely determine offsets on active faults. A second and equally demanding requirement for determining long-term slip rates, however, is that offset strata or landforms must be reliably dated, and existing methods for dating geologically young surfaces and strata only partially meet this demand. A novel technique for determining the age of landforms offset by faulting will be developed and applied in this research project. Specifically, the project will extend and further develop small-sample, high precision 230Th/U dating of soil carbonate via mass spectrometry. The results will provide unprecedented insight into the constancy (or lack thereof) of slip rates over time on the Elsinore fault, a principal strand of the San Andreas fault system in southern California, over a range of intervals in the past approximately 100,000 to 200,000 years.The research project will further develop a novel means of dating geologically youthful landforms, extend the capacity and capability of earth scientists to determine fault slip rates in arid regions worldwide, and help to address societal needs for more quantitative assessment of seismic hazards. The project will also provide comprehensive training in innovative techniques of geochronology for doctoral candidate.

大陆板边界通常由宽阔的变形区域组成，其特征在于由多个，大约平行断层（例如加利福尼亚州的San Andreas断层系统）组成的断层系统。为了更好地量化这种断层造成的地震危害，必须确定其通过时间的运动模式。虽然板边界断层系统附近观察结果的最新进展提供了对相对短（即际际时期）上地壳变形模式的前所未有的洞察力，但可能会在更长的时间尺度上表现出可变的位移速率。也就是说，从大地数据中得出的滑移速率可能反映了最近与大地震相关的瞬态运动，或者是最近的其他地壳负荷变化。在较长的时间尺度上，认为主要断层（例如南加州圣安德烈亚斯）的滑移率在过去大约100，000年内的差异约为两倍。如果确认，这种变异性可能是由于不断发展的地壳结构复杂性，中间时间尺度（即大约10，000年）或其他机制的地震聚集而导致的。因此，量化1至100，000年的时间尺度上的断层滑移率是对大陆动力学的改善理解的基础，并将满足社会需求，以改善主要断层系统附近的地震危害的定量。然而，在1到100，000年的时间尺度上，故障滑移的可靠测量非常有限。这部分是由于地质情况的相对稀有性，这些情况保留了确切确定主动断层的偏移所需的适当地层或地貌信息。但是，确定长期滑移率的第二个也是如此的要求，是必须可靠地进行偏移层或地面的日期，而现有的约会地质年轻表面和地层的方法仅部分满足了这一需求。该研究项目将开发和应用一种用于确定地形被断层弥补的新型技术。具体而言，该项目将通过质谱法扩展并进一步发展土壤碳酸盐的高精度230/U年代。结果将为埃尔西诺尔故障（Elsinore Wurd）上的恒定率（或缺乏稳定性）提供前所未有的见解，这是南加州南加州的主要链，在过去的一系列间隔中，大约100,000至200,000年的间隔。该研究项目将进一步开发出一个新颖的能力，以扩大地球的能力，以扩大了地球的能力，以扩大了地球的能力，并延伸了地球的能力，以实现地球上的能力，以实现地球的能力，以实现地球上的能力，并将其延长，以下地球上的地球上的能力，构成了地球上的能力，该项目构成了旨在的，并将其延长，以下方面的地球，并将其延长，以下地球上的地球上的能力，并将其确定，以下方面的地球上的能力，构成了地球的能力。解决社会需求，以进行更定量的地震危害评估。该项目还将为博士候选人的创新技术提供全面的培训。