Simultaneous imaging of BSR for gas hydrate exploration and ocean current fine structures

A Multi-Channel Seismic (MCS) data was used for imaging Bottom Simulating Reflectors (BSRs) and ocean current fine structure features across a 215 km long-offset seismic data (MGL0905-01) collected under TAIGER project in southwestern Taiwan. The MCS seismic data was collected during early April 2009 and was used to investigate both targets features across the continental slope margin which has background geologic characteristics across passive to active margins. Conventional seismic processing strategy and Kirchhoff post-stack time migration were applied to create the final stacked seismic profile. The deconvolution is applied to remove airgun source signature, increase frequency bandwidth and enhance both ocean current and BSRs structure features. The distribution of the BSRs are identified which varied between 0.3 and 0.5 s two-way travel-time (TWTT) below seafloor. The image of ocean current structures revealed two major ocean current layers. Near-surface currents are characterized by continuous, nearly horizontal stratified layers with smoothly and laterally varying dipping reflectors indicates obvious air-sea surface interaction features. More apparent wavy shaped, less continuous with varying in impedance contrast, relative strong top and bottom reflections with relatively low internal amplitude reveal the feature related to eddy currents can be identified in the intermediate depth. The image also clearly revealed the physical processes related to internal waves and eddy currents may strongly affected by sea-floor topography. Through investigations of FK spectral contents, transmission and gain analyses, the spatial distribution features of identifiable current types including internal waves and wave energy features are all helpful in promoting our observation and understanding of ocean structure and dynamic processes involved across different scale constrained by seismic frequency band.