Estudio sísmico-acústico del gas somero en la zona externa de la Ría de Arousa (NW de España)

Resumo

Detailed analysis of geophysical profiles (high resolution seismic reflection, side-scan sonar and echo-sounder) have permitted detecting and characterizing the presence of gas within the sediments of the external-part of the Rfa de Arousa (NW Spain). Gas accumulations are clearly detectable from high resolution records in the sedimentary infill of the rfa. Results reveal the presence of three main types of gas accumulations: acoustic blanking s.s., with a flat top and an average lateral extent of 800 m; acoustic curtains, with convex top and a lateral extent from WO m to 200 m; and acoustic columns, acoustically transparent and with a lateral extent less than 100 metres. The analysis of side-scan sonar, 3.5 kHz and echo-sounder records reveals that two patterns of gas seeps (acoustic plumes and pockmarks) can be established and mapped in the study area. Finally, the depth of the gas accumulation areas was mapped. Their origin and possible control factors for their special distribution are discussed.