Computational Methods for Most-Energetic Traveltimes of Seismic Waves

地震波最高能量走时的计算方法

• 批准号: 0107210
• 负责人: Seongjai Kim
• 金额: $ 3.86万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0107210&HistoricalAwards=false
• 关键词: Computational; Methods; Most; Energetic; Traveltimes

The work is concerned with the development of computational methods for the most-energetic traveltimes (METTs) of seismic waves and their applications to various physical problems. The METT corresponds to the highest energy level in data and has been recognized as one of most important components for image/inversion processes in highly heterogeneous media. However, METTs often develop discontinuities in wavefronts. Thus, computational principles that have been utilized for the computation of continuous first-arrival traveltimes can hardly be adopted. The upwind direction of the METT is determined by the energy level (amplitudes) of wavefronts and, therefore, the amplitude accuracy is very crucial for a successful METT simulation. Since the transport equation, which solves the amplitude, incorporates the traveltime Laplacian, the traveltime should be solved by a non-oscillatory high-order numerical algorithm which can provide a mechanism for an accurate traveltime Laplacian near the discontinuities. The investigator proposes the development of accurate and efficient algorithms for the METT and the corresponding amplitude in 3D heterogeneous media, incorporating second- and third-order ENO schemes and their local extensions for intersecting wavefronts near discontinuities. A full wavefield solver of negligible numerical dissipation is to be developed and implemented for a numerical verification of the conjecture: the METT can be computed in such a way that the corresponding amplitude is continuous over the whole domain. Applications are planned for the anisotropic METT and realistic geophysical problems such as tomography in oil exploration, earthquake analysis, and shallow seismic reflection. The proposed research subjects are vitally important to energy, economic, and environmental concerns. In particular, the theoretical understanding and numerical algorithms for the METT and the corresponding amplitude will open other promising research areas.For various applications of sound waves traveling through a substance, it is necessary to compute the traveltime of the sound waves. Since the acquired data are dominated by the highest energy levels of the waves, the most reliable results can be obtained by incorporating information from the most-energetic traveltime (METT). The proposal is concerned with the development of accurate and efficient computational algorithms for the METT and applications to important geophysical image processing problems. Image processing methods allow geoscientists to find interesting underground features. In oil exploration, for example, geophysicists first compute images of rock/soil structures and then detect the spots where oil reservoirs are. Thus the oil reservoir detection can be successful only with accurate and well-focused images, for which the newly developed algorithms provide the most useful information. The same arguments can be applied to the shallow sound wave reflection, the image processing techniques for the subsurface not deeper than 100 meters. These techniques have been developed for detailed images; examples can be found in waste-disposal site characterization, archaeological search, and ground security analysis. Many cracks and break-downs on buildings or roads are due to an ignorance or under-estimation of the importance of ground security analysis. The proposed work is also applicable to earthquake analysis. Since a horrible destruction happens with a close relation to the most-energetic components of the earthquake wave, the computation of the METT is necessary for a deeper understanding of the earthquake. The new algorithms are expected to provide an effective mechanism that helps geoscientists simulate seismic ground motion and helps geologists predict earthquake destruction areas, with high accuracy and efficiency. The above mentioned problems are vitally important to energy, economic, and environmental concerns and can be solved more reliably by the proposed work.

这项工作涉及地震波最高能量旅行时(MET)计算方法的发展及其在各种物理问题中的应用。Mett对应于数据中的最高能级，被认为是高度非均质介质中成像/反演过程中最重要的组成部分之一。然而，梅特经常在波前出现不连续现象。因此，用于计算连续首达旅行时间的计算原理几乎不能被采用。Mett的迎风方向由波前的能级(振幅)决定，因此，振幅的精度对Mett模拟的成功至关重要。由于求解振幅的输运方程包含了旅行时拉普拉斯算子，因此旅行时方程应采用非振荡的高阶数值算法来求解，这样才能在不连续面附近提供精确的旅行时拉普拉斯算子。研究人员提出了在三维非均匀介质中，结合二阶和三阶ENO格式以及它们的局部扩展，以求在不连续面附近相交波前的准确和高效的算法。开发并实现了一个可忽略数值耗散的全波场求解器，用于对这一猜想进行数值验证：Mett可以这样计算，即相应的幅度在整个区域内是连续的。各向异性大地电磁和现实地球物理问题，如层析成像在石油勘探、地震分析和浅层地震反射中的应用正在计划中。拟议的研究主题对能源、经济和环境问题至关重要。特别是，对介电常数及其振幅的理论理解和数值算法将开辟其他有前途的研究领域。对于声波在物质中传播的各种应用，计算声波的旅行时是必要的。由于所获取的数据主要是波的最高能级，因此可以通过结合来自最高能量旅行时(Mett)的信息来获得最可靠的结果。该提案涉及为Mett开发准确和高效的计算算法，并将其应用于重要的地球物理图像处理问题。图像处理方法使地球科学家能够发现有趣的地下特征。例如，在石油勘探中，地球物理学家首先计算岩石/土壤结构的图像，然后检测储油层所在的地点。因此，只有准确和聚焦良好的图像才能成功地进行油藏检测，而新开发的算法为这些图像提供了最有用的信息。同样的论点也适用于浅层声波反射，即地下深度不超过100米的图像处理技术。这些技术已经被开发用于详细的图像；可以在垃圾处理场地的描述、考古搜索和地面安全分析中找到例子。建筑物或道路上的许多裂缝和故障都是由于忽视或低估了地面安全分析的重要性。建议的工作也适用于地震分析。由于可怕的破坏发生与地震波中能量最高的分量密切相关，因此计算Mett对于加深对地震的了解是必要的。预计新算法将提供一种有效的机制，帮助地学家模拟地震地面运动，并帮助地质学家预测地震破坏区域，精度和效率都很高。上述问题对能源、经济和环境问题至关重要，拟议的工作可以更可靠地解决这些问题。