基于构造系统函数的大地电磁时间序列模拟方法

MT time series simulation based on constructed system function

大地电磁(MT)作为一种有效的地球物理勘探手段,观测数据的去噪和阻抗估算是重要的处理环节,使用模拟电磁场时间序列验证时间域阻抗估计和后续信号处理方法很有必要。本文基于构造的系统函数,由随机序列的离散傅里叶变换(DFT)获得频率域磁场数据,结合正演模型阻抗计算频率域电场数据,最后对频率域电磁场单边谱和阻抗序列做复共轭对称处理,经快速反傅里叶变换(IFFT)获得模拟的电磁场时间序列。研究结果表明,该方法可适用于一维和二维水平非均匀介质电阻率模型的时间序列模拟,对比实测数据表明,由该方法得到的电磁场数据能够较好地体现MT数据的频谱特性。

For magnetotelluric(MT)method,an effective geophysical tool,data impedance estimation and noise elimination are key steps,which have great influence on the impedance characteristics.So it is necessary to test impedance estimation and subsequently signal processing in the time domain with simulated electromagnetic time series.Based on constructed system function,the magnetic field in the frequency domain is obtained by the discrete Fourier transform(DFT)of random sequence,and the electric field in the frequency domain is calculated with model impedance and simulated magnetic field.Finally,the symmetry processing of complex conjugate is performed on the unilateral spectrum of electromagnetic field and the impedance sequence in the frequency domain,and the simulated time series of electromagnetic field is obtained with inverse fast Fourier transform(IFFT).Test results show that the proposed method can be used to simulate the time series of one-dimensional and two-dimensional horizontal heterogeneous model,and compared with measured data,the electromagnetic field data obtained with this method can better reflect MT frequency spectrum characteristics.