科研之友
微信
新浪微博
Facebook
分享链接
摘要
In the conventional CSEM exploration method, only main frequencies of signal are used, or some lower-order harmonics information is extracted based on experiences. But such a procedure has no criteria to valid information extracted. In this paper we present an effective method for evaluating noise influence in the frequency domain, which makes it possible to extract frequency coefficients with high SNR, including both the main frequency and its harmonics. The spectrum of raw data is obtained from time domain data by using the mix-radix fast Fourier transform. Then it puts the amplitude of CSEM frequency into the average of adjacent two frequencies to output a modified spectrum. This pre-processed spectrum is divided into low frequency part (trend) and high frequency part (oscillation) by using discrete wavelet transform. The analytic envelope of the high frequency part is obtained based on Hilbert transform. The upper bound curve of the total spectrum is reconstructed with the low frequency part and the envelope of high frequency part. The maximum influence amplitudes (MIA) of noise at CSEM frequencies are estimated. Noise evaluation number is calculated based on MIA and raw amplitude in CSEM frequency. By this noise rating number, it will be possible to screen out frequency coefficients with high SNR from raw spectrum. By applying this method, amount of frequency coefficients, including many high-order harmonics, are extracted without increasing any field work. Vertical resolution of CSEM is also improved by this method since more frequency coefficients are extracted.
- 出版日期2018-1
- 单位中南大学
