A seismic field test with a Low level Acoustic Combustion Source and Pseudo Noise codes

Abstract

The Low level Acoustic Combustion Source (LACS) is a new type of pulsed underwater acoustic source with an output level of 0.5-1.0 barm peak to peak. The source is based on a combustion engine and intended for shallow seismic surveys. It operates at 5 m depth and is able to fire pulses at a rate of up to 11 shots per second. Because of the source’s low output level, it is expected to be more suitable than other sources in environmental sensitive areas. The low pulse level may be compensated for by an integration of energy from a sequence of pulses. This article describes the results of a seismic field test in Byfjorden outside Bergen, Norway. The best seismic result is achieved using deconvolution or an iterative correlation method where the correlator sequence is recorded right below the seismic source. Compared with airgun results along the same survey path, the seismic picture based on the LACS source gives a clearer presentation of the bottom layers.