Abstract

Delineating finer details of sub-surface is always a challenge, particularly in complex geological provinces such as the thrust fold belt and subvolcanic regions from seismic traveltime tomography only. Further the traveltime modeling has a limited resolution in the order of Fresnel zone, whereas the state-of-the-art seismic full waveform tomography (FWT), which can exploit entire components (traveltime, amplitudes, frequencies, phases...) of data, can delineate finer details of the subsurface. We have successfully imaged the long-wavelength subsurface velocity models using traveltime tomography (TT) to the first arrival ocean bottom seismic (OBS) data along two cross lines in the Kerala - Konkan (KK) offshore basin. Further, we have employed the FWT to the same OBS data using the TT model as initial model to demonstrate the efficacy and practical feasibility of this modern tool that still lies at the nascent stage of development. The tomographic velocity images show the smooth velocity variations from 1.5 km/s to 7.1 km/s. The velocity-depth functions match quite accurately with the available high-frequency VSP velocity-depth function at well-A and well-B drilled within the study area