Research On The Influence Of Square Wave Noises On Magnetotelluric Remote Reference Method

Magnetotelluric(MT) sounding meathod utilizes the propagation characteristics of natural electromagnetic field to study the geological structure in depth. Magnetotelluric transfer functions were calculated from measurements of horizontal electric and magnetic fields at the surface of the earth. MT signals are so week that often contaminated with noise from natural or man-made processes that may lead to serious errors in computed MT transfer functions. Magnetotelluric remote reference(RR) methods is one way to deal with the local noise in magnetic fields. The bias in the magnetic field is eliminated by using the cross-spectrum with a remote site instead of the autopower. The method was proposed by Gamble at1979and now developed to be a rapidly widely practical application method with the development of GPS satellite synchronization technologyThe paper designed seven simulation square waves, formed three groups of contrast in three aspect:width, spacing and amplitude. Using the open source code written by Egbert and the uniform half space time series, the paper calculated the influenced sounding curves and remote reference curves, examines the effect of different kinds of square wave noise in detail and summarizes a series of noise impact and remote reference method of denoising. The simulation results show that the remote reference method is an effective way to eliminate the effects of square wave noise. The result of RR method was influenced by the noise amplitude, width, signal-to-noise ratio and coherence between noise and remote reference state. The paper combines the audio-magnetotelluric measured data of Tong Ling&Lu Zong region data to verify the simulation results. Conclusions of the paper have a profound significance to actual data processing.