ИСТИНА

The Shillong plateau, also known as the Meghalaya plateau, is one of the highly seismically active regions, spanning an area of approximately 25,000 km^2. It is composed of Archean gneissic basement rocks, indicated by a high Bouguer anomaly. The structure lies between the Himalayan collision zone to the north and the Indo-Burmese subduction zone to the east. As a result, it experiences significant tectonic forces from both directions, which have contributed to its uplift since the Tertiary period. Tectonically, it is bounded by the Dauki fault to the south, the Brahmaputra fault system to the north, the Kopili fault to the East, and the Dhubri fault to the west. The geoelectrical properties of this region were investigated using the magnetotelluric method (MT), where broadband data were acquired at 16 stations and long-period data at 7 stations. The profile crossed two faults, namely the Dudhnoi Fault and the Oldham Fault, with the epicentre of the 1897 Shillong earthquake, which had elevated the plateau by approximately 10 meters. Most seismic activities in the region are confined to depths of 35 km, extending to 45-50 km. The processing of the MT data was performed using MAPROS and SigMT for Broadband and Geomag for the LMT data, as well as with Russian PRC_MTMV and EPI-Kit software. The sounding curves showed lower resistivity values (between 10 - 1 ohm-m) on some stations along the profiles. Thus, the need to analyse the dimensionality and directionality became crucial for the interpretation. The swift skew was somewhat effective for interpretation, but the Bahr skew showed predominantly a 3D nature, with some 1D and 2D behaviours (mostly in higher frequencies). The phase tensor skew value is abnormally high (β=10 ) at stations near or beneath the Oldham fault and Dudhnoi fault, suggesting their presence. The strike directions also vary near the faults and at some other stations, indicating the complexity of the region, and would require further modelling to examine them.