Collaborative Research: CMG Research: Statistical Seismic Imaging

合作研究：CMG 研究：统计地震成像

• 批准号: 0222181
• 负责人: Susan Minkoff
• 金额: $ 19.27万
• 依托单位: University of Maryland Baltimore County
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0222181&HistoricalAwards=false
• 关键词: Collaborative; Research; CMG; Statistical; Seismic

Collaborative Research: CMG Research: Statistical Seismic ImagingA. Levander, W.W. Symes, S. MinkoffBoth the crystalline crust and the shallow near surface ( 100m depth) environment are complex, mechanically heterogeneous regions, often having spatial distributions of mechanical properties that are distinctly different from the relatively smoothly layered sedimentary column. Exploration seismology is currently one of the most important means of exploring the subsurface: for petroleum in the sedimentary column, for geotechnical/environmental purposes in the shallow subsurface, and for understanding of tectonic processes in the crystalline crust. Reflection seismology was developed by the petroleum industry to explore the sedimentary column, i.e., the medium is layered, the preponderance of energy is singly scattered, and scales are dichotomous. Its applications in both the near-surface environment and the deep crust have been very successful but also present problems not usually encountered in petroleum exploration. The near surface is subjected to chemical and mechanical weathering processes that produce a highly heterogeneous, nonlayered medium. Mechanical properties can vary by an order of magnitude within a few wavelengths due to compaction, chemical alteration, and the presence or absence of water. The crystalline crust, although lacking order of magnitude changes in mechanical properties, has a spatially complex, often self-affine (fractal) distribution of seismic velocity and density heterogeneities. For the relatively long path propagation in the crust, the wavefield often falls in a strong scattering regime in which linear imaging systems will produce mediocre or nonsensical results.This research program makes first steps toward a complementary imaging paradigm for complex media, termed statistical seismic imaging, in which statistical properties of the subsurface are mapped using statistical properties of the seismic wavefield. As this is an extremely large topic, the proposal scope will be limited to a few areas of endeavor. The investigations will explore (1) effective models relating subwavelength scale heterogeneity to macro-scale propagation effects (effective mechanical properties, velocity, attenuation, dispersion, etc), (2) the extent to which multiple reflection and refraction can be differentiated and their effects on traditional seismic imaging, and (3) the identification of the onset of strong scattering. The research involves a high level of software development and computational effort, including 3D seismic simulation and nonlinear inversion for material properties and statistics. No single discipline possesses the tools to make significant progress on statistical seismic imaging: expertise in geophysics, applied math, and high performance computing are needed. The principal investigators have expertise in these areas. The research has the potential of improving societally important environmental/geotechnical investigations as well as more fundamental research on the structure and tectonics of the Earth's crust.

合作研究：CMG研究：统计地震成像A。结晶性地壳和浅层(100米深)环境都是复杂的、机械不均匀的区域，其力学性能的空间分布往往与相对平滑的层状沉积柱截然不同。勘探地震学目前是勘探地下的最重要手段之一：在沉积柱中寻找石油，在浅层地下出于岩土/环境目的，以及了解结晶地壳中的构造过程。反射地震学是石油工业为了勘探沉积柱而发展起来的，即介质是层状的，能量优势是单一分散的，尺度是二分的。它在近地表环境和深部地壳中的应用都是非常成功的，但也存在着石油勘探中不常遇到的问题。近地表经历了化学和机械风化过程，产生了高度不均匀的非层状介质。由于压实、化学变化和水的存在或不存在，机械性能在几个波长内可能会有一个数量级的变化。结晶性地壳虽然在力学性质上没有数量级的变化，但在空间上具有复杂的、通常是自仿射(分形)的地震速度和密度不均匀分布。对于在地壳中传播的较长路径，波场往往处于强散射区域，线性成像系统将产生平庸或无意义的结果。本研究计划朝着复杂介质的互补成像范式迈出了第一步，称为统计地震成像，其中地下的统计特性利用地震波场的统计特性来映射。由于这是一个非常大的主题，建议的范围将限于几个努力领域。这些研究将探索(1)亚波长尺度非均质性与宏观尺度传播效应(有效力学性质、速度、衰减、色散等)之间的有效模型，(2)可区分多次反射和折射的程度及其对传统地震成像的影响，以及(3)强散射开始的识别。这项研究涉及高水平的软件开发和计算工作，包括三维地震模拟和材料特性和统计的非线性反演。没有一门学科拥有在统计地震成像方面取得重大进展的工具：需要地球物理、应用数学和高性能计算方面的专业知识。主要调查人员在这些领域拥有专业知识。这项研究有可能改进具有重要社会意义的环境/岩土调查，以及更多关于地壳结构和构造的基础性研究。