Modeling of terrain effect in magnetotelluric data from Garhwal Himalaya Region

Abstract. The magnetotelluric method (MT) is one of the most effective geophysical techniques for studying the deep structure of the Earth's crust, particularly in steep terrain like the Garhwal Himalaya region. The MT responses are distorted as a result of the undulated/rugged terrain. Such responses, if not corrected, can lead to a misinterpretation of MT data for the geoelectrical structures. In this research paper, two different correction procedures were used to compute the topography distortion for the synthetic model of Garhwal Himalaya region from Roorkee to Gangotri section. A finite difference algorithm was used to compute MT responses (apparent resistivity and phase) for the irregular terrain. The accuracy of the terrain correction procedures was checked on results published in the literature on different topography models at various periods. The relative errors between flat earth response (FER) and two terrain correction procedures (TCR1 and TCR2) were calculated and were very less or almost zero for most of the sites along the Roorkee to Gangotri profile except at the foothill where the error was high at lower periods. The similar topography response, terrain corrected responses TCR1 and TCR2 responses concluded that there is no need for topography correction along Roorkee-Gangotri Profile because the slope angle is less than one degree.