Acoustic system for physical oceanography research in deep ocean

Abstract

Marine multichannel seismic (MCS) data, used to obtain structural reflection images of the Earth’s subsurface, can also be used in physical oceanography exploration. This method provides vertical and lateral resolutions of 10 to 100 m, to full ocean depth, along profiles that can be hundreds of kms in length, covering the existing observational gap in oceanic exploration. All MCS data used so far in physical oceanography studies have been acquired using conventional seismic instrumentation originally designed for geological exploration. In this work we present the proof of concept of an alternative MCS system that is better adapted to physical oceanography and has two goals: (1) to have an environmentally low impact acoustic source to minimize any potential disturbance to marine life, and (2) to be light and portable. The synthetic experiments simulate the main variables of the source, shooting and streamer that compose the proposed MCS system. The proposed system utilizes a 5 s long exponential chirp source of 208 dB re 1micro Pa @ 1m with a frequency content of 20-100 Hz, and a relatively short 500-m long streamer with 100 channels. We exemplify through numerical simulations that the 5 s long chirp source can reduce the peak of the pressure signal by 26 dB with respect to equivalent airgun-based sources by spreading the energy in time, greatly reducing the impact to marine life. Additionally, the proposed system could be transported and installed in mid-size oceanographic vessel, opening new horizons in acoustic oceanography research.