THE TIME-DOMAIN MAGNETOTELLURIC RESPONSE OVER 3-LAYER EARTH MODELS

Magnetotelluric data observed in frequency and time domains are expres sed as apparent resistivity. The apparent resistivity is a weighted sp atial average of the subsurface resistivity distribution. In this pape r, we develop analytical expressions to compute the apparent resistivi ty in the time domain for various three-layer earth models. The presen t approach to computing the magnetotelluric response in the time domai n is found to overcome the problems encountered by the method of image s. The magnetotelluric response in the time domain for various three-l evel models have been computed and shown graphically. The time-domain responses show a characteristic behaviour with a small change in layer ed parameters (resistivity and thickness of the layers), whereas frequ ency-domain responses do not show such behaviour. This characteristic behaviour of time-domain magnetotelluric sounding curves will be usefu l in the qualitative interpretation of field data.