Sub-basalt sediment imaging — The efficacy of magnetotellurics

•Usefulness of magnetotellurics in imaging sub-basalt sediments•In trap covered areas the MT alone produces highly dependable subsurface models.•Constrained inversion of MT data for conductive overburden case gives a realistic model.

While magnetotellurics (MT) is known to be successful in detection of subtrappean sediments in trap (basalt) covered areas like Saurashtra, India, we further evaluate its efficacy for estimation of subsurface models in combination with borehole and seismic data. For this purpose, we consider two different geological scenarios represented by two types of areas in India: one-trap covered area like the Saurashtra peninsula and the other where the trap itself is overlain by conductive sedimentary column represented by the Cambay basin. It is shown from inversion of synthetic as well as real data that in the first case (i.e., solely trap covered areas), the MT alone produces highly dependable subsurface models, while in the second case (i.e., trap overlain by conductive sediments), a constrained inversion of MT data using inputs from seismic/borehole results for overlying Tertiary sediment thickness, provides a more realistic sub-basalt subsurface model than that retrievable from any one of the individual methodologies.