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针对常用大地电磁(magnetotelluric,MT)信号小波阈值去噪中阈值函数和阈值选取的不足,选取一种新的阈值函数,并提出了基于小波变换多分辨Stein无偏风险估计,自适应的获得最优阈值的方法;给出了新函数和自适应阈值的确定方法;在与小波硬、软阈值去噪、小波模极大值法去噪结果对比的基础上,用仿真实验验证了方法的可行性;最后用内蒙某地实测的大地电磁数据进行了去噪效果的对比研究.结果表明:本文选取的新函数和自适应阈值的确定方法是正确、有效的,克服了常用小波硬、软阈值去噪的缺点;去噪后大地电磁信号变得平稳,估算的响应参数方差减小,曲线更为圆滑、连续,为后续的地质解释和评价提供了更为准确的信息.
Aiming at the shortcomings of threshold function and threshold selection in the commonly used magnetotelluric (MT) signal wavelet denoising, a new threshold function is selected and a multi-resolution Stein unbiased risk estimation based on wavelet transform is proposed. The method to determine the optimal threshold and threshold value is given. The method of determining the new function and adaptive threshold is given. Based on the comparison with the wavelet hard and soft threshold denoising and wavelet modulus maxima method, the simulation results show that the method is feasible Finally, a comparative study on the denoising effect of the measured data from a local area in Inner Mongolia was carried out. The results show that the new function and the method of determining the adaptive threshold are correct and effective, and overcome the common wavelet hard and soft threshold Denoising; the denoised earth electromagnetic signal becomes stable, the estimated variance of the response parameter decreases, the curve is more smooth and continuous, which provides more accurate information for subsequent geological interpretation and evaluation.