Abstract The Fourier analysis is conventional technique for approximating the frequency content of earthquake ground motions. These approaches assume that earthquake excitation is a stationary process. Time frequency analysis techniques such as wavelet transform consider an earthquake to be a non-stationary process that shows a variation in frequency content over time, but these techniques are not easy to apply and most engineers are not familiar with their sophisticated mathematics. This paper introduces a new method for investigating of frequency content of earthquake records which is more accurate than Fourier spectrum but yet easy to apply for structural design and seismological studies. The efficiency of this new approach is investigated by analyzing a variety of single and multiple degree of freedom systems against near, mid and far field earthquake components. The results demonstrate the efficiency of the proposed method for a range of systems having different natural fundamental periods.

中文翻译：

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对傅里叶变换的改进以提高其在地震信号频率内容评估中的性能

摘要 傅里叶分析是近似地震动频率成分的常规技术。这些方法假设地震激发是一个平稳过程。时频分析技术（如小波变换）将地震视为一个非平稳过程，其频率内容随时间发生变化，但这些技术并不容易应用，而且大多数工程师并不熟悉其复杂的数学知识。本文介绍了一种新的地震记录频率成分调查方法，该方法比傅立叶谱更准确，但易于应用于结构设计和地震学研究。通过分析各种单自由度和多自由度系统对近、中远场地震分量。结果证明了所提出的方法对于具有不同自然基本周期的一系列系统的效率。