Combined Normal-Incidence and Wide-Angle Reflection Studies of the Lower Crust and Moho

下地壳和莫霍面的法向入射和广角反射相结合的研究

• 批准号: 8708597
• 负责人: Scott Smithson
• 金额: $ 27.03万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-10-01 至 1991-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8708597&HistoricalAwards=false
• 关键词: Combined; Normal; Incidence; Wide; Angle

The nature of the lower crust, Moho, and upper mantle is the major uncertainty in the genesis of continental lithosphere, and recent studies have indicated major differences in these among different tectonic provinces. A series of normal incidence and wide-angle recording experiments involving discontinuous expanding spread profiles around common depth points. The normal-incidence data will determine the detailed layering and the wide-angle data will resolve the velocity structure and whether it is sharp or gradational. S-wave data will be recorded to make combined P-and S-wave interpretations for fluid content and lithology. Areas to be studied include the Basin and Range where strong subhorizontal lower-crustal and Moho reflections are found, an accreted terrain in NE Washington where many arcuate lower crustal reflections and some clear discontinuous Moho reflections occur, Archean-Proterozoic transitional crust (overprinted during the Laramide?) in SE Wyoming with sporadic lower crustal and questionable Moho reflections, Proterozoic crust in Kansas with abundant arcuate lower crustal reflection pattern and no Moho reflections. These areas provide widely varying tectonic regimes, ages, and differences in reflection response that must indicate different structure. Completed pilot studies show that lower crustal velocity structure can be resolved in NE Nevada to address the question of the "double Moho reflection," and that a Moho reflection is seen at 80 km range in SE Wyoming but not observed at normal incidence. Processing will be based on a combination of standard reflection processing and new approaches for improving S/N, tau-P analysis, and migration. These studies will provide a relatively accurate and detailed velocity profile and also mean crustal velocity which can be related to tectonic history and continental growth.

下地壳、莫霍面和上地幔的性质是 大陆岩石圈成因的重大不确定性， 最近的研究表明， 不同的构造区 一系列垂直入射和 涉及不连续的广角记录实验 扩展围绕共同深度点的扩展配置文件。 的 正常发病率数据将确定详细的分层， 广角数据将解析速度结构， 无论是尖锐的还是渐变的。 将记录S波数据 对流体含量进行纵横波联合解释 和岩性。 研究范围包括盆地和山脉 强烈的近水平下地壳和莫霍面反射 在华盛顿东北部发现了一个增生的地形， 下地壳反射和一些明显的不连续莫霍面 反射发生，太古宙-元古代过渡地壳 （在Laramide期间叠印？）在东南怀俄明州， 元古代下地壳和可疑莫霍面反射 堪萨斯地壳，具有丰富的弧形下地壳反射 没有莫霍面反射 这些地区广泛提供 不同的构造体制、时代和反射的差异 必须指示不同结构的响应。 完成试点 研究表明，下地壳速度结构可以 在东北内华达州解决了“双莫霍面”问题 反射，”和莫霍面反射被认为是在80公里范围内， 怀俄明州东南部，但在正常发病率下未观察到。 处理将 基于标准反射处理的组合， 改善S/N、tau-P分析和偏移的新方法。 这些研究将提供一个相对准确和详细的 速度剖面和平均地壳速度， 与构造历史和大陆生长有关。