A New Approach for Rapidly Transient Evolutionary Seismic Spectral Analysis

快速瞬态演化地震谱分析的新方法

• 批准号: 9615897
• 负责人: Theodore Wu
• 金额: $ 23.89万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-02-15 至 2000-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9615897&HistoricalAwards=false
• 关键词: New; Approach; Rapidly; Transient; Evolutionary

A new method, the Hilbert-Huang Technique (HHT), is being developed to perform analysis of highly transient time series from nonlinear, dispersive, and nonstationary systems. Such data as typical of records on natural disasters for which the conventional Fourier and Fourier-akin (such as the various wavelet schemes) have severe drawbacks. This new method consists of two parts: the Intrinsic-Mode Decomposition (IMP) scheme, and the Hilbert Spectral Analysis (HSA) technique. The IMD generates the Intrinsic Base Functions from the raw data; and the HSA then concerts the IBF into an energy-frequency-time distribution through the Hilbert transform. The result yields the Hilbert Spectrum depending on both time and time varying-frequency as two spectral independent variables. This project will conduct the following research: First, a thorough understanding of the physical characteristics of the HHT in seismic data analysis will be established. For this purpose, both rigorous theoretical analyses and controlled laboratory tests will conducted. Second, the HHT method will be applied to seismic data and explore the potential applications in the specific take of determining site-specific spectra. Data collected during the Northridge earthquake (1994) and those collected from Taiwan including the SMART-l and SMART-2 network will be used. Specific tasks include: (a) To derive accurate information on strong-motion and weak-motion evolutions due to the geophysical effects along the paths of propagation, and the site effects on seismic waves. (b) To determine the energy-frequency-time history of the seismic activities and their response spectra; to evaluate the nonlinear wave evolution and surface wave dispersion due to complex earth structure. (c) To clarify the role of the suspected excessive vertical motion by comparison with the known earthquake damages. (d) To establish a methodology for evaluating the site-specific spectra based on the HHT and the data analyzed above. The data will be classified by their sources and grouped by the seismic strengths to isolate the propagation effects through earthquakes of all sizes. Specific attention will be on the identification of propagation path and site-specific geo-engineering properties of the site.

Hilbert-Huang技术（HHT）是一种新的方法，用于分析非线性、色散和非平稳系统的高暂态时间序列。这些数据是典型的自然灾害记录，传统的傅立叶和傅立叶相似（如各种小波方案）有严重的缺点。该方法由本征模分解（IMP）和希尔伯特谱分析（HSA）两部分组成。IMD从原始数据生成固有基函数；然后HSA通过希尔伯特变换将IBF调合成能量-频率-时间分布。结果得出希尔伯特谱依赖于时变频率和时变频率作为两个谱独立变量。本项目将进行以下研究：一是在地震资料分析中全面了解高温高压的物理特征。为此目的，将进行严格的理论分析和受控的实验室试验。其次，将HHT方法应用于地震数据，探索在确定特异位点谱的具体领域的潜在应用。将使用1994年北岭地震期间收集的数据和从台湾收集的数据，包括smart - 1和SMART-2网络。具体任务包括：(a)获得由于沿传播路径的地球物理效应和地震波的场址效应而引起的强震和弱震演变的准确资料。(b)确定地震活动的能量频率-时间历史及其反应谱；研究复杂地球结构下的非线性波演化和表面波频散。(c)通过与已知地震损害的比较，澄清怀疑的过度垂直运动的作用。(d)根据HHT和上面分析的数据建立评价特定地点光谱的方法。这些数据将按其来源分类，并按地震强度分组，以隔离各种大小地震的传播效应。特别注意的是传播路径的确定和场地特定的地质工程特性。