Magnetotelluric investigations in the southern end of the Cambay basin (near coast), Gujarat, India

Abstract

Cambay basin is one of the major onshore oil-bearing sedimentary basins of India situated at its western margin in Gujarat state. The region is seismically active and experiences three devastating earthquakes in the past. The region comes under the seismic zone IV and V and necessitates the extensive geophysical studies in for subsurface characteristics and identification of hidden faults in the region for seismic hazard estimation. A magnetotelluric (MT) survey has carried out in the southwestern part of the Cambay basin to identify the sedimentary thickness, the depth of Deccan trap and for identification of West Cambay margin that passes through the region. The MT data, at 13 stations, in the broad frequency range is acquired along an east-west profile with an inter-station spacing of 2–3 km. After processing and analysis of the data, transfer functions in the period band of 0.001–300 s are used for two-dimensional joint inversion. The resultant structure from the 2-D modeling infers the sedimentary thickness of ~0.5 km. A high conductive zone dipping towards east observed in the eastern part of the profile might be due to the West Cambay fault. Basement fracturing at a depth of 2.5–3.0 km at the central portion of the profile might act as a heat exchanger between the deeper geothermal source and nearby hot water spring.