A seismic modelling study for Antarctic subglacial lake exploration

The recent interest of Antarctic research on subglacial lakes requires a better understanding of their geological context, i.e., their relation to basement structures, the mechanism of the sedimentary processes, and the possible occurrence of free-gas or gas-hydrate bearing layers. The multichannel seismic method is a useful investigation tool for these purposes. This study was undertaken to provide a procedure for designing suitable seismic surveys, aimed at determining the location and the morphology of Antarctic subglacial lakes by employing a reasonable amount of resources. This procedure involves numerical simulation of synthetic seismograms, AVO analysis, ray-tracing and travel-time tomography. In particular, we applied this methodology to the seismic characterisation of Lake Vostok, and the following optimal basic configuration is advisable: two arrays of 6 geophones spaced at 100 m intervals, the first one placed at 500 m from the source and the second one at 3 km from the source. Shifting both source and arrays 1 km away after each shot, we are able to obtain a sufficient ray coverage at the bottom of the lake, and define the ice-water, water-sediment and sediment-bedrock interfaces with an accuracy of about 16 m. This study also provides a general methodology for optimising seismic surveys.