EXTENDED MARINE ARRAYS VERSUS SIMULATED EXTENDED ARRAYS*

Abstract

ABSTRACTTwo factors are responsible for the fact that an extended marine source array performs better than a point source:1. a higher degree of transmission of the radiated seismic energy through the water‐sediment interface providing a better penetration;2. filtering effects.The higher degree of transmission is due to: (a) the directivity of extended sources, (b) the lower reflection coefficient at the water‐sediment interface for seismic waves radiated from an extended source array than for spherical seismic waves radiated from a point source, (c) the lower amplitude decay of the pulses from an extended source than from a point source. In addition, signature characteristic of an extended source array and Fresnel zone of waves generated by such a source differ from those corresponding to a point source.The propagating wavelet radiated from a point source array may not be, in a sedimentary sequence below the sea‐floor, the linear combination of wavelets emitted from point sources. In such cases, there is a noticeable difference between the performance of a field‐implemented source array and that of the corresponding simulated source array. The performances of the field‐implemented and simulated extended receiver arrays can be identical if the recording system is adequate and the processing technique appropriate.