Plate 111

Injection structures: pockmark

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Pockmarks are pits on the sea bed representing the superficial expression of large-scale gas vents. The example shown here is a seismic section recorded in the Adriatic Sea by a 3.5 kHz subbottom profiler. The geometry of the vent cannot be resolved in this record because of distortion of reflected waves ("hyperbolic echoes"), but is visible as a discontinuity (with downward inflections) in buried reflectors.

The deep beds from which the gas derives are not reached by acoustic waves, which have been absorbed by overlying layers.

Glossary