Design of a Hum Filter for Suppressing Power-line Noise in Seismic Data

A unique filtering approach designed to eliminate power-line noise on shallow seismic data without affecting the frequency content of signal provides a powerful harmonic noise suppression tool for data acquired with modern large dynamic range recording systems. The filter is determined by the Levenberg-Marquardt (L-M) method using records present before the first arrivals. Initial amplitudes of sinusoids (functions of power-line noise) are determined in the frequency domain using fast Fourier transform methods while initial phases are obtained by time domain correlation. Modeling results suggest the relative error of these initial estimates is less than 50 percent. Well-defined initial values guarantee convergence of the L-M method. Calculation efficiency is achieved by simplifying the L-M solution using the singular value decomposition technique. The approach can handle cases where power-line noise with frequencies of 60Hz and∕or its multiples (120Hz, 180Hz, and 240Hz, etc.) exist simultaneously. Once de...