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

下地壳、莫霍和上地幔的性质是大陆岩石圈成因的主要不确定性，最近的研究表明，不同构造省在这些方面存在重大差异。围绕共深点的不连续扩展扩散剖面的一系列正入射和广角记录实验。正入射数据将确定详细的分层，广角数据将确定速度结构以及速度结构是尖锐的还是渐变的。将记录s波数据，对流体含量和岩性进行纵波和s波联合解释。要研究的区域包括盆地和山脉，在那里发现了强烈的亚水平下地壳和莫霍反射，在华盛顿东北部的一个增加地形，那里有许多弧形的下地壳反射和一些明显的不连续的莫霍反射，怀俄明东南部太古宙-元古代过渡地壳（Laramide期间叠印）下地壳零星，莫霍反射可疑；堪萨斯州元古代地壳下地壳弧形反射模式丰富，无莫霍反射。这些地区提供了广泛不同的构造制度，年龄和反射响应的差异，必须表明不同的结构。已完成的初步研究表明，在内华达州东北部可以解决较低的地壳速度结构，以解决“双莫霍反射”的问题，并且在怀俄明州东南部80公里范围内可以看到莫霍反射，但在正常入射下没有观察到。处理将基于标准反射处理和改进信噪比、tau-P分析和偏移的新方法的结合。这些研究将提供相对准确和详细的速度剖面，以及与构造历史和大陆生长有关的平均地壳速度。

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.