Abstract
<p>Rolling array pattern broad band magnetotelluric (MT) data was acquired in the Koyna-Warna (Maharashtra, India) seismic zone during 2012-14 field campaigns. The main objective of this study is to identify the thickness of the Deccan trap in and around the Koyna-Warna seismic zone and to delineate the electrical nature of the sub-basalt. The MT data at many places got contaminated with high tension power line noise due to Koyna hydroelectric power project. So, in the present study an attempt has been made to tackle this problem due to 50 Hz noise and their harmonics and other cultural noise using commercially available processing software MAPROS. Remote site was running during the entire field period to stand against the cultural noise problem. This study is based on Fast Fourier Transform (FFT) and mainly focuses on the behaviour of different processing parameters, their interrelations and the influences of different processing methods concerning improvement of the S/N ratio of noisy data. Our study suggests that no single processing approach can give desirable transfer functions, however combination of different processing approaches may be adopted while processing culturally affected noisy data.</p>
Highlights
Magnetotelluric (MT) is a passive electromagnetic (EM) geophysical method to delineate the subsurface resistivity structure
To obtain a desirable MT transfer function from time series which is highly contaminated with cultural noise was our prime objective
Remote reference technique can handle this situation until the remote site is free from any kind of noise
Summary
Magnetotelluric (MT) is a passive electromagnetic (EM) geophysical method to delineate the subsurface resistivity structure. RR technique can improve the data quality if the cultural noise associated with the local and remote sites is uncorrelated [Clarke et al 1983, Ritter et al 1998, Uchida et al 2005, Weckmann et al 2005]. For the short period data it was a challenge to process and derive a reasonable transfer function. In this present study, instead of looking for a new method we mainly concentrated on the methods which are already exist and try to study the behaviour of different processing parameters, their role and the interrelations among them regarding improvement of the S/N ratio using commercially available processing software, MAPROS [Friedrichs 2007]. During our study we have applied different processing approaches, viz. Selective
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