Reflected acoustic energy from geological layers during seismic reflection surveys

Area of Science:

• Geophysics
• Ocean Acoustics
• Marine Seismic Exploration

Background:

• Seabed characteristics critically affect acoustic propagation modeling.
• Shallow seabed properties are well-studied, but deep seabed characteristics are often overlooked.
• Deep seabed layers influence low-frequency acoustic signals below 100 Hz.

Purpose of the Study:

• To investigate the impact of deep seabed characteristics on acoustic propagation.
• To quantify the contribution of sub-seabed layers to reflected acoustic energy.
• To analyze the relationship between layer depth and reflected energy.

Main Methods:

• Analysis of marine seismic reflection survey data (MGL2104).
• Utilized a 5700 in.3 airgun array and a 1200-channel streamer (∼15 km).
• Examined acoustic reflections in one-third-octave bands below 100 Hz.

Main Results:

• Sub-seabed layers contribute significantly (>50% at times) to reflected energy below 100 Hz.
• Seafloor reflections dominate only at ranges near the critical angle.
• Increased sub-seabed layer depth does not always decrease reflected energy.

Conclusions:

• Deep seabed layers play a crucial role in low-frequency acoustic propagation modeling.
• Ignoring sub-seabed characteristics can lead to inaccuracies in acoustic propagation models.
• Further research into deep seabed impacts on acoustics is warranted.