Shallow Geophysical Characterization and Fluid Flow Processes in Two Large Pockmarks on the Malin Shelf, NW Ireland

Abstract

Shallow geophysical datasets and ground-truthing have been used in this research to characterize in detail two large gas related depressions in a recently discovered pockmark field on the Malin Shelf, northwest Ireland. Pockmarks are aligned to the main deep fault of the region, the SW-NE Skerryvore Fault. High resolution multibeam bathymetry and backscatter reveal the surface morphology of these seabed features to the meter scale. They appear as subcircular depressions and present several units within a generally smooth seabed. Shallow seismic and single-beam echosounder records reveal evidence of gas related activity within the subsurface strata. Electromagnetic results present a number of anomalies in conductivity associated with inhomogenities in the upper strata. These anomalies consist in a decrease in conductivity and in general, correlate well with acoustic anomalies.