Acoustic observation, identification, and scattering intensity measurement of cold seep based on bubble resonance

Abstract

The active “cold seep” is indisputable evidence to identify the existence of submarine gas hydrate. Due to the difference in acoustic properties between cold seep bubbles and surrounding seawater, measuring scattering intensity is a new means to detect active cold seep. Cold seep bubbles are the main cause of acoustic scattering, and the scattering ability is closely related to the frequency of the incident sound wave, the radius of the bubble, and the depth of the bubble. This article introduces a ship-borne cold seep sonar system, which uses the resonance principle of bubbles to measure the scattering intensity at various depths underwater and display it with an intuitive acoustic image. Through the investigation and measurement of the cold seep located in the South China Sea, it is proven that the cold seep sonar system can well identify the submarine cold seep. The measured data are consistent with the theoretical simulation results, confirming that the cold seep bubbles have frequency-selective characteristics for incident sound waves. Compared with other detection methods, it has the characteristics of lossless, fast, and high efficiency.