Imaging shallow gas migration pathways in a mud-volcano province using an autonomous underwater vehicle (Malta Plateau, Mediterranean Sea)

A. Savini, S. Pinson, A. Bistacchi, G. Etiope, Charles Holland

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Data acquired by an autonomous underwater vehicle (AUV) towing a source (1600-3500 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 pseudo-three-dimensional coverage of the study area, with a horizontal and vertical resolution of roughly 3-5 m and 5-10 m, respectively. This map was combined with high-resolution 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 Plio-Quaternary 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.

Original languageEnglish (US)
Pages (from-to)681-699
Number of pages19
JournalNear Surface Geophysics
Volume16
Issue number6
DOIs
StatePublished - Jan 1 2018

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Malta
underwater vehicles
Mediterranean Sea
mud volcano
autonomous underwater vehicle
mud
volcanoes
plateaus
plateau
gases
gas
fault zone
sediments
scattering
towing
acoustic data
hydrophone
hydrophones
slug
complex systems

All Science Journal Classification (ASJC) codes

  • Geophysics

Cite this

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abstract = "Data acquired by an autonomous underwater vehicle (AUV) towing a source (1600-3500 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 pseudo-three-dimensional coverage of the study area, with a horizontal and vertical resolution of roughly 3-5 m and 5-10 m, respectively. This map was combined with high-resolution 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 Plio-Quaternary 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.",
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Imaging shallow gas migration pathways in a mud-volcano province using an autonomous underwater vehicle (Malta Plateau, Mediterranean Sea). / Savini, A.; Pinson, S.; Bistacchi, A.; Etiope, G.; Holland, Charles.

In: Near Surface Geophysics, Vol. 16, No. 6, 01.01.2018, p. 681-699.

Research output: Contribution to journalArticle

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