广义S变换时频域滤波在MT数据处理中的应用

摘要

短时傅里叶变换是建立在稳态信号基础之上,它仅能提供信号的频域信息,对信号的时间分辨能力差.这影响了它在大地电磁测深数据处理中的应用效果.S变换是一种优于短时傅立叶变换的时频分析方法,能够提供信号时-频域信息.利用S变换对大地电磁测深数据进行时频分析,有助于实现大地电磁测深数据噪声的时频-域滤波,从而提高大地电、磁分量数据的频谱分析精度.从广义S变换理论出发,分析了各类波形噪声的时-频域特征及其对大地电磁测深数据的影响.针对大地电磁测深数据处理特点,利用广义S变换得到时频谱,采用时频比值和门槛值方法,研究适合压制电磁噪声的时频滤波器和滤波方法.对实际大地电磁测深数据的处理结果表明这个方法提高了阻抗张量的估算质量,验证了该方法的有效性.%Short-time Fourier transform is founded on the base of stationary signal analysis and can provide information in frequency domain with a bad ability of signal analysis in time domain. S transform is one of methods of signal analysis in time-frequency domain, which is better than short-time Fourier transform, and can provide information of signal in time-frequency domain. By using S transform to analyze Magnetotelluric (MT) sounding data in time-frequency domain, it is helpful to filter noise in MT data and to improve the quality of MT data spectrum. This paper studied the method of time-frequency domain filtering for suppressing noise in magnetotelluric sounding data by the generalized S transformation. Time-frequency characteristics of noises of all kinds of wave and theirs influence are analyzed. According to the MT data processing characteristics and GST spectrum, time-frequency filter and filter method are studied, which is suitable for suppressing the MT noises. Through actual MT data processing, the quality of impedance tensor estimate is improved and validity of the proposed method is verified.