Long-range acoustic scattering from a shallow-water mud-volcano cluster

Area of Science:

• Oceanography
• Acoustics
• Geology

Background:

• Reverberation measurements in the Straits of Sicily exhibit anomalous high-intensity scattered returns.
• These returns deviate significantly from background noise, suggesting a distinct source.

Purpose of the Study:

• To analyze acoustic reverberation patterns in the Straits of Sicily.
• To identify the source of discrete, high-intensity scattered returns.
• To characterize the acoustic scattering properties of mud volcanoes.

Main Methods:

• Analysis of in-situ reverberation measurements.
• Statistical characterization of acoustic returns.
• Estimation of target strengths over a range of frequencies (160-1400 Hz).

Main Results:

• Discrete scattered returns, 10-20 dB above background, were attributed to mud volcanoes.
• Reverberation was consistent over spatial (kilometers) and temporal (hours, years) scales.
• Non-Rayleigh statistics indicated mud volcanoes as a likely source of clutter.
• Carbonate chimneys (approx. 10m diameter, several meters high) on mud volcanoes were identified as the primary scattering mechanism.

Conclusions:

• Mud volcanoes, particularly their carbonate chimneys, are significant sources of acoustic scattering and clutter.
• The scattering is characterized by non-Rayleigh statistics and is consistent across various scales.
• These findings are crucial for understanding acoustic propagation and target detection in environments with mud volcano activity.