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2-D velocity structure in Kerala-Konkan basin using traveltime inversion of seismic data

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Journal of the Geological Society of India

Abstract

The existence of gas-hydrates in marine sediments increases the seismic velocity, whereas even a small amount of underlying free-gas reduces the velocity considerably. The change in velocities against the background (without gas-hydrates and free-gas) velocity can be used for identification and assessment of gas-hydrates. Traveltime inversion of identifiable reflections from large offset multi channel seismic (MCS) experiment is an effective method to derive the 2-D velocity structure in an area. We apply this method along a seismic line in the Kerala-Konkan (KK) offshore basin for delineating the gas-hydrates and free-gas bearing sediments across a bottom simulating reflector (BSR). The result reveals a four layer 2-D shallow velocity model with the topmost sedimentary layer having velocity of 1,680–1,740 m/s and thickness of 140–190 m. The velocity of the second layer of uniform thickness (110 m) varies from 1,890 to 1,950 m/s. The third layer, exhibiting higher velocity of 2,100–2,180 m/s, is interpreted as the gas-hydrates bearing sediment, the thickness of which is estimated as 100 to 150 m. The underlying sedimentary layer shows a reduction in seismic velocity between 1,620 to 1,720 m/s. This low-velocity layer with 160–200 m thickness may be due to the presence of free-gas below the gas-hydrates layer.

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  1. CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad, 500 007, India

    Praveen Kumar Singh & Kalachand Sain

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  1. Praveen Kumar Singh
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  2. Kalachand Sain
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Correspondence to Kalachand Sain.

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Singh, P.K., Sain, K. 2-D velocity structure in Kerala-Konkan basin using traveltime inversion of seismic data. J Geol Soc India 79, 53–60 (2012). https://doi.org/10.1007/s12594-012-0006-2

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  • DOI: https://doi.org/10.1007/s12594-012-0006-2

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