Physics-based characterization of soft marine sediments using vector sensors

Area of Science:

• Geophysics
• Ocean Acoustics
• Marine Seismology

Background:

• Seismo-acoustic wave fields are crucial for understanding seafloor properties.
• Interface waves propagate along boundaries and carry information about sediment layers.
• Previous studies have explored marine sediment characterization using wave phenomena.

Purpose of the Study:

• To analyze low-frequency seismo-acoustic wave fields in the northern North Sea.
• To investigate the characteristics of interface waves and their relation to seabed structure.
• To develop a geoacoustic model that explains observed seismo-acoustic phenomena.

Main Methods:

• Deployment of a linear horizontal array of seafloor vector sensors.
• Analysis of power spectra to identify dominant frequencies and wave phenomena.
• Examination of dispersion curves for interface waves to infer sediment properties.
• Development and application of a geoacoustic model for inverse problem analysis.

Main Results:

• Observation of a strong, narrow power spectrum peak around 38 Hz.
• Identification of multi-mode horizontally and vertically polarized interface waves.
• Phase speeds for interface waves ranged from 45 to 350 m/s.
• Dispersion curves indicated a two-layered seabed with power-law shear speed dependence.
• A geoacoustic model successfully reproduced key observational features.

Conclusions:

• The observed power spectrum peak is interpreted as a seismo-acoustic resonance.
• The findings suggest a complex, layered marine sediment structure.
• The developed geoacoustic model provides a quantitative explanation for the observations.
• Vector sensor data is critical for separating wave polarizations and evaluating sediment density.