Estimation of magnetotelluric transfer functions in the time domain over a wide frequency band

Abstract

SUMMARY Determination of the transfer function is the main objective in magnetotelluric (MT) and geomagnetic data processing. In this paper we describe a new algorithm for finding a transfer function through determination of the impulse response in the time domain. The proposed method was developed for the long time-series with which we are usually dealing in short-period recording. It allows the determination of the transfer function for a broad range of frequencies, the only limitation being the duration of recording. In contrast to other methods for determination of the time-domain transfer function we selected an approximation of impulse response in which the number of unknowns to be determined is proportional to the frequency range of interest on a logarithmic scale. This is a natural way to deal with functions such as the MT impedance tensor or geomagnetic vector. Our approximation makes it easy to find the predicted electric field, which is very useful for assessing the quality of the recorded data.