A powerline noise suppression scheme for the acquisition and processing of CSAMT data

Abstract

The recordings of controlled source audio electromagnetic (CSAMT) are invariably contaminated with powerline noise, which seriously impedes the application of CSAMT in densely populated areas. Based on the integer-period cancellation, a powerline noise suppression scheme is described for CSAMT data acquisition and processing. The essence of this scheme is to choose reasonable transmitting frequencies and window lengths of spectrum estimation. According to the specified power transmission standard, a set of CSAMT transmitting-receiving frequencies and sampling lengths can be designed. The effective amplitude and phase can be estimated through dividing the pre-filtered soundings into specified segments for spectrum estimation and Robust stacking. Without involving the magnetic field that is more sensitive to noise, the electric field component is directly converted into the full-field apparent resistivity directly to obtain geoelectric feature. Synthetic and field examples indicate that the nonstandard powerline noise can be effectively suppressed. This scheme can be easily embedded in most of the modern instrumentations, and extend application conditions to high cultural noise areas.