Disturbances On Magnetotelluric Data Due To Electrified Railway

Magnetotelluric (MT) soundings were made on two transverse profiles to the Campos do Jordão Railway (CJR) in the<br>period range of 4 to 3000s. The profiles are located in two adjacent regions of the São Paulo State with contrasting<br>conductivity: the conductive sedimentary region of Taubaté Basin and the resistive crystalline region of Serra da<br>Mantiqueira. The data were collected during diurnal and nocturnal periods, when the CJR operates with DC current and<br>when it is turned off, respectively. The objective of this study is to attempt to eliminate the electromagnetic noise<br>produced by the CJR in the diurnal data. To achieve this goal we plan to use some techniques based on the MT<br>response function estimation and then to estimate the resistivity profile of the region. This profile will be compared with<br>the results obtained from nocturnal data, not contaminated with the noise of the CJR, to verify the relative efficacy of the<br>methods employed to filter out the electromagnetic noise. The preliminary results indicate that the Serra da Mantiqueira<br>region is 177.8 times more resistive than the Basin and that the skin depth in the Basin is of 2.7 km.