Exploring surface source contributions to ocean ambient noise interferometry with airgun shots

Area of Science:

• Geophysics
• Ocean Acoustics
• Seismology

Background:

• Ambient noise interferometry is a powerful tool for seismic imaging.
• Understanding source location effects is crucial for accurate seismic data interpretation.
• Ocean acoustic environments present unique challenges for seismic studies.

Purpose of the Study:

• To investigate how the location of surface sound sources influences ambient noise interferometry.
• To analyze the spatial contributions to cross-correlations between two hydrophones.
• To understand the role of surface and bottom reflections in seismic interferometry.

Main Methods:

• Conducted a seismic reflection survey over two bottom-mounted hydrophones in the northeast Pacific.
• Utilized airgun shots as discrete, impulsive sound sources.
• Performed simulated and experimental analyses of cross-correlations.

Main Results:

• Demonstrated that surface source locations directly affect ambient noise interferometry results.
• Identified contributions to cross-correlations arising from ocean surface and bottom reflections.
• Provided insights into the emergence of the Green's function from ambient noise.

Conclusions:

• Surface source characteristics are critical for interpreting ambient noise interferometry data.
• Reflections play a significant role in shaping the cross-correlations observed between hydrophones.
• The study clarifies limitations and possibilities in inferring seismic properties from ambient noise.