Seismic Imaging of Southern Californian Crust Using Deformable-Layer Tomography and Prestack Depth Migration

使用变形层断层扫描和叠前深度偏移对南加州地壳进行地震成像

• 批准号: 0814013
• 负责人: Hua-Wei Zhou
• 金额: --
• 依托单位: Texas Tech University
• 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: 2007-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0814013&HistoricalAwards=false
• 关键词: Seismic; Imaging; Southern; Californian; Crust

To advance our understanding of the crustal structure and geodynamics of southern California, a new crustal seismic imaging project is carried out to significantly improve the mapping of the regional 3D crustal velocity structure and major reflection events across the San Andres fault system. The data include the earthquake readings compiled by the Southern California Earthquake Center (SCEC) and seismic reflection records from the Los Angeles Regional Seismic Experiment (LARSE). An innovation of the project is the use of a new deformable-layer tomography to directly map the geometry of P-wave and S-wave velocity discontinuities in the crust and uppermost mantle, and constrained by known crustal thickness variations from receiver functions and other analyses. In addition, an advanced wave equation prestack depth migration is applied to provide new reflection images for the LARSE profiles. The preliminary results from this project indicate that the new tomography method produces sharper vertical resolution and more realistic representations of lens-shaped geologic features like the edges of basins and lithologic pinchouts, which is a significant improvement over traditional tomography that inverts for velocity values on fixed-in-space mesh grids. The LARSE reflection images obtained so far indicate that prestack depth migration can better handle near surface lateral velocity variations and improve the resolution and reflector continuity over previous images of the LARSE datasets. Interestingly, the results from this project suggest that the presence of high noise level, strong lateral velocity heterogeneity and crooked survey geometry argue for, rather than against, the use of prestack depth imaging over the simple CMP stack techniques. This two-year project is expected to provide significantly improved 3D P-wave and S-wave crustal velocity models for southern California and prestack depth migrated images beneath two onshore LARSE surveys across the San Andres fault system. The broader impacts of the project include field demonstration of innovative seismic imaging techniques for future crustal and mantle studies, such as those envisioned for EarthScope/USArray, as well as promotion of crossbreeding in ideas and training between solid Earth geophysics and exploration geophysics that will lead to a fundamental modification of undergraduate and graduate education in seismic imaging.

为了提高我们对南加州地壳结构和地球动力学的认识，进行了一个新的地壳地震成像项目，以显着提高整个圣安德烈斯断层系统的区域三维地壳速度结构和主要反射事件的映射。 这些数据包括南加州地震中心（SCEC）编制的地震读数和洛杉矶区域地震实验（LARSE）的地震反射记录。 该项目的一个创新是使用新的可变形层层析成像技术，直接绘制地壳和上地幔中P波和S波速度不连续的几何图形，并受接收器功能和其他分析得出的已知地壳厚度变化的限制。 此外，还应用了一种先进的波动方程叠前深度偏移方法，为LARSE剖面提供了新的反射图像。 该项目的初步结果表明，新的层析成像方法产生了更清晰的垂直分辨率和更真实的透镜状地质特征，如盆地边缘和岩性尖灭，这是一个显着的改进，传统的层析成像，在固定的空间网格上反演速度值。 到目前为止获得的LARSE反射图像表明，叠前深度偏移可以更好地处理近地表横向速度变化，并提高分辨率和反射连续性比以前的图像的LARSE数据集。 有趣的是，该项目的结果表明，存在高噪声水平，强烈的横向速度不均匀性和弯曲的测量几何主张，而不是反对，使用叠前深度成像的简单CMP叠加技术。 这个为期两年的项目预计将提供显着改进的三维P波和S波地壳速度模型为南加州和叠前深度偏移图像下的两个陆上LARSE调查整个圣安德烈斯断层系统。 该项目更广泛的影响包括：实地演示用于未来地壳和地幔研究的创新地震成像技术，如EarthScope/USAray设想的技术，以及促进固体地球物理学和勘探地球物理学之间的思想和培训杂交，这将导致地震成像本科和研究生教育的根本改变。