A Study On CSAMT Synthetic Aperture Method

The controllable source audio magnetotelluric method is an artificial source frequency domain electric sounding method developed on the basis of the audio magnetotelluric method.It has a large detection depth,strong anti-interference ability,and a very good recognition of low resistance abnormal bodies and faults.Its characteristics have been widely used in the fields of production and scientific research.Firstly,starting from the Maxwell equations,and derive the frequency of the electric and magnetic fields coupled differential equations,differential discretized using biquadratic interpolation of continuous functions,obtained function value of each node to meet the of linear algebraic equations,the coefficient matrix of the one-dimensional nonzero elements of austerity storage,the use of large-scale sparse matrix parallel solvers PARDISO solving this complex coefficient symmetric linear equations,obtaine d under the excitation of the artificial source geoelectric section in two-dimensional wave number domain response to electromagnetic fields.Finally select the appropriate wave number of the inverse Fourier transform,namely,obtaining the spatial domain response.Afterwards,the nonlinear conjugate gradient algorithm(NLCG)is used to perform two-dimensional inversion on the forward data.In order to optimize the forward and inversion effects,enhance the abnormal response amplitude and improve the detection accuracy,this paper introduces the method of controllable source audio magnetotelluric synthetic aperture technology,and applies the high-frequency electromagnetic synthetic aperture radar technology to frequency-based applications.In the controllable source diffusion equation of the domain,it is not necessary to perform the wave field transformation,but rather the interference principle of the diffusion field.The concept of synthetic aperture comes from synthetic aperture radar.Because the signals between adjacent measuring points of the same geological body have the characteristics of correlation,the signal of the neighboring measuring points is correlated and superimposed to achieve improvement.Signal-to-noise ratio,outliers,and anomalous anomalies have further improved the resolution.At the same time,this processing method also develops the conventionally used single-point-based processing method as a method for processing multiple points-by-point multiple coverage with the measurement point as the center.By selecting the optimal amplitude,phase shift weighting coefficients and synthesis range for inverse synthesis,we can maximize the abnormal amplitude and enhance the resolution of the target without changing the acquisition method and increasing the exploration cost.In this paper,the optimal amplitude and phase shift weighting coefficient of the synthetic aperture and the synthetic aperture range are selected using the experimental method.By designing multiple theoretical models,the synthetic aperture method is compared with the unsynthesized data.The results show that the synthetic aperture method can effectively improve the abnormal response amplitude and detection effect.