Title: Novel applications of broad band near sea floor pressure/acoustic monitoring for time lapse remote sensing of sea-bed processes
Researchers: Dr Florian Le Pape, Prof. Chris Bean
Acoustic signals are trapped in the water column and communicate with the sub-surface geology through acoustic-to-elastic wave conversions. Near sea floor acoustic signals can also be used as a shallow sediment imaging tool (without the need to shoot seismics) for instance, near sea floor structure but also time lapse sea floor monitoring (using acoustic waves to estimate sediment stiffness changes). A major part of the broad band acoustic signal is the ocean wave induced acoustic noise which generates pressure fluctuation at the sea floor converted into seismic noise or also called microseisms. Understanding ocean generated seismic noise sources and propagation is very important as ‘ambient noise correlation’ techniques can be used for broad (regional) scale seismic passive imagery and time-lapse monitoring (e.g. in reservoirs). Microseisms can also be used for ocean storm tracking and for determining areas of maximum cyclical pressure fluctuations on the sea floor.
What are the sediments and water column effects on secondary microseisms generation an propagation? What are the characteristics of the associated wavefield through strong seismic/acoustic coupling?
Objectives are: (i) background mapping of the broad band acoustic landscape in the marine environment – previous work has not looked at very low frequency acoustics (ii) determine to what extend acoustic noise in the water (that noise which is derived from viscoelastic wave conversions at the sea floor from seismic background wave propagation from the solid geology into the water column) can be used to map ‘shallow’ geological structure below the sea floor.