Tectonic appraisal of the Mid-Thane Creek of Mumbai, India: An integrated geophysical approach

Integrated geophysical surveys, comprising marine magnetic, high resolution shallow seismic and single-beam bathymetry were conducted to assess subsurface tectonics of the Mid-Thane Creek (MTC) of Mumbai. The bathymetry in the intertidal zone of MTC varies drastically due to periodic dredging, with maximum depth up to 6.4 m and a minimum of ~−1.6 m. High resolution shallow seismic sections up to the depth of ~35 m from the sea-floor are generated to analyze the neotectonic activity of the creek. Imprints of deep-seated lineaments are recognized from magnetic anomaly map of the MTC. To delimit lateral extent of the lineaments/faults, results of several derivative methods including tilt derivative and standard Euler deconvolution are merged with the selected crest value of the horizontal derivative. To estimate depth to the source, Euler deconvolution, tilt derivative, analytic signal, and source parameter imaging method have been used. However, the depth estimation for the lineaments/faults is highly discrepant for this region, because of the complex tectonics associated with the periodic emplacements of Deccan flood basalt. To confine the top and bottom boundary of this highly magnetized basaltic layer, we have carried out spectral analysis considering 18 windows of 2000 × 2000 m with an overlap of 500 m. The average depth to the top and bottom of the source body estimated using spectral analysis is consistent with the depth estimated from the derivative filters. This confirms that the lineaments identified by the derivative filters may embed in the basaltic layer of MTC. The most prominent lineament interpreted from the seismic and magnetic data, in the central region of MTC is inferred as the marine analogue of Alibagh–Uran Fault passing through the mainland of Alibagh and Uran close to Mumbai city. Highlights Acquired, processed and interpreted high resolution shallow seismic, marine magnetic, single beam bathymetry data in the Mid-Thane creek of Mumbai, India. Neo-tectonic and deep-seated tectonic elements are identified using the seismic and magnetic data. Identification of the faults/lineaments and source depth estimation are performed using total horizontal, analytic signal, tilt derivative, Euler deconvolution and source parameter imaging derivative methods. Thickness of the flood basalt where the faults/lineaments are embedded is estimated using spectral analysis. Interpreting the marine extension of Alibagh–Uran fault zone in the Mid-Thane creek of Mumbai, India.