Preliminary Results of an Evaluation of the Efficiency of VLF Seismic Propagation in a Continental Slope Environment

Data collected in a continental slope geometry were used to investigate the efficiency of low frequency bottom penetrating propagation. Preliminary ray trace and bottom los modeling were used to estimate the duration of the water-borne component of shot data and to identify shots containing potential sediment penetrating arrivals. Frequency band analysis of the time series of a shot was used to confirm the identification of a subbottom penetrating arrival on the basis of its loss of high frequency energy due to absorption within the subbottom. Propagation loss, estimated using the theoretical source spectrum, was used to compare low frequency propagation along a subbottom path to high frequency propagation along a waterborne path. This comparison showed that for a source in deep water and a bottomed receiver on the continental slope, the efficiency of 35 Hz bottom penetrating propagation is comparable to, if not better than, propagation along a waterborne path over the 35-1000 Hz frequency range studied. (Author)