4 research outputs found
Imaging shallow gas migration pathways in a mudâvolcano province using an autonomous underwater vehicle (Malta Plateau, Mediterranean Sea)
Data acquired by an autonomous underwater vehicle (AUV) towing a source (1600â3500 Hz) and a horizontal array of hydrophones have been analysed to image discrete, isolated or even a small cluster of scatterers within the sediment, to determine shallow migration paths of hydrocarbons in a mud volcano system of the Malta Plateau. An algorithm based on a semblance function was applied to the acoustic data to highlight scatterers rather than interface reflections. The resulting scatterer map, obtained along the AUV track, generated a pseudoâthreeâdimensional coverage of the study area, with a horizontal and vertical resolution of roughly 3â5 m and 5â10 m, respectively. This map was combined with highâresolution bathymetric and backscattering seafloor maps obtained from previous explorations. This integrated dataset provides new evidence for the role of fault zones as a preferential path for gas/fluid migration and reveals the intermittent activity of seeping gas. The data show, in particular, that gas bubble slugs, i.e. discontinuous gas columns, rise through PlioâQuaternary sediments along a complex system of conduits terminating at the surface into quiescent mud volcanoes. The gas flux is facilitated by the regional stress field that results in dilatant conditions on the mapped fault zones