Collaborative Research: Late Cenozoic Vertical Crustal Motions and Erosional Mass Transfer in the Southern San Andreas Fault Zone

合作研究：圣安德烈亚斯断裂带南部的晚新生代地壳垂直运动和侵蚀质量传递

• 批准号: 1145115
• 负责人: James Spotila
• 金额: $ 7.74万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-15 至 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1145115&HistoricalAwards=false
• 关键词: Collaborative; Research; Late; Cenozoic; Vertical

Vertical crustal motions are widely recognized in continental strike-slip fault zones, yet the underlying controls and surficial response to 3-dimensional strain in these settings are poorly understood. Observed patterns of uplift and subsidence often do no match the predictions of numerical models for oblique strain, suggesting that existing models for strike-slip faults are incomplete. Structural controls on development of sedimentary basins in strike-slip fault zones are similarly complex and incompletely understood. This project is addressing these problems with a multi-disciplinary, multi-investigator study of 3-dimensional strain and related surface processes in the San Andreas fault zone of southern California. The research team will use a diverse suite of methods to document rates and geometries of vertical crustal motions through time, and test two hypotheses for the evolution of the San Andreas fault: (1) that plate-motion obliquity exerts the primary control on the 3-dimensional and temporal evolution of the fault zone; and (2) that the fault zone experienced a major change at approximately 1.1 to 1.4 million years ago in response to tectonic reorganization of the plate boundary. Each hypothesis makes unique predictions about space-time patterns of uplift, erosion, subsidence, and sediment dispersal within the fault zone, that will allow the team to test the hypotheses with a systematic program of fieldwork, data analysis, and modeling. This project integrates diverse research methods including geologic mapping, stratigraphic and structural analysis, paleomagnetic studies of sediment age and block rotations, provenance analysis, detrital zircon dating, low-temperature (U-Th)/He dating of bedrock sources, geomorphic analysis, study of seismic and gravity data, and numerical modeling.This study seeks to fill large gaps in the understanding of the geologic evolution of the southern San Andreas fault system, a complex network of seismically active faults that define the Pacific-North America plate boundary in California. The history of deformation over geologic timescales (millions of years) is relatively poorly known, despite its critical role in shaping the crustal architecture and fault geometries that control earthquakes in this setting. This project's approach benefits from a unique collaboration of academic researchers and students from four universities with earth scientists at the U.S. Geological Survey. The team is also collaborating with geophysicists investigating processes of continental rupture beneath the Salton Sea, and scientists studying paleoseismology and fault slip rates on the San Andreas fault over shorter timescales. These collaborations provide an important avenue for engaging with and contributing new knowledge to the vibrant geoscience community in southern California. Lessons learned in this research will be used to develop new lab and teaching exercises that will reach thousands of students over the course of the project. Ultimately, the results of this study will shed new insights into dynamic linkages between crustal deformation, fault-zone complexity, growth of topography, erosion, and sediment dispersal within continental strike-slip fault zones at active plate boundaries.

垂直的地壳运动在大陆走滑断层区域被广泛认可，但是在这些环境中，对3维应变的潜在控制和表面反应却鲜为人知。观察到的抬高和沉降模式通常与斜应菌株数值模型的预测不符，这表明现有的走滑断层模型是不完整的。对走滑断层区域中沉积盆地发展的结构控制同样复杂且尚不完全理解。该项目通过对南加州圣安德烈亚斯断层区的三维应变和相关表面过程进行多学科的多学科研究来解决这些问题。研究小组将使用各种方法来记录随时间的垂直地壳运动的速率和几何形状，并检验两个假设，以证明圣安德烈亚斯断层的演变：（1）板倾斜的倾斜度对断层区的3维和时间演变产生了主要控制； （2）断层区在大约1.1至140万年前经历了重大变化，以响应板块边界的构造重组。每个假设都对断层区域内的隆升，侵蚀，沉降和沉积物分散的时空模式做出了独特的预测，这将使团队能够通过系统的现场工作，数据分析和建模来测试假设。该项目整合了多种研究方法，包括地质映射，地层和结构分析，对沉积物年龄和阻滞旋转的古磁研究，出处分析，碎屑锆石的预期，低体温（U-TH）/基地的测定/基地的日期，基地来源，地位和地质分析，地理位置和严重的研究，以寻求地震范围的研究，以填补范围的研究，以填补范围的范围，以填充该模型，以填充该模型的范围。 Southern San Andreas断层系统是一个复杂的地震活跃断层网络，定义了加利福尼亚州太平洋北美板块边界。地质时间尺度（数百万年）的变形史相对较少，尽管在塑造在这种情况下控制地震的地壳结构和断层几何形状方面的重要作用。该项目的方法受益于美国地质调查局的四所大学与地球科学家的学术研究人员和学生的独特合作。该团队还与地球物理学家合作调查了萨尔顿海下方的大陆破裂过程，科学家研究了较短的时间表上圣安德烈亚斯故障上的古代学和断层滑移率。这些合作为参与并为南加州的充满活力的地球科学社区提供新知识提供了重要的途径。在这项研究中汲取的教训将用于开发新的实验室和教学练习，这些练习将在整个项目的过程中吸引成千上万的学生。最终，这项研究的结果将提供对地壳变形，断层区的复杂性，地形的生长，侵蚀和沉积物分散在大陆板边界处的大陆走滑断层区域内的动态联系的新见解。