Inversion for Geoacoustic Model Parameters in Complex Oceanic Environments
Abstract
Approved for Public Release The long term objectives of this research project are to assess performance and understand limitations of simple and effective experimental methods and inversion techniques that provide estimates of parameters of geoacoustic models of the ocean bottom and their associated uncertainties. The wider context of this research is related to the development of improved sonar system performance aided by greater understanding of the physics of the interaction of sound with the ocean bottom. The research proposed here is based on the investigation of model-based geoacoustic inversion methods. The work is focused on three aspects: (1) Assessment impulsive sound sources for use at high frequencies: With recent new opportunities to use small explosive charges as sound sources in experiments at higher frequencies, there is a need to understand the characteristics of the source waveform at frequencies greater than 1 kHz, and establish accurate source spectrum levels.The main objective is to understand the cause of a secondary pulse immediately following the shock wave. (2) Impact of shear waves on geoacoustic inversion for model parameters of marine sediment: Most inversions that have been carried out assume a fluid sediment model. The research question is whether neglect of shear waves has an impact on the estimated model parameters. The more technical challenge is to design an appropriate approach for making a quantitative assessment of the impact. (3) Impact of model mismatch in geoacoustic inversion: Model-based inversion techniquesare fundamentally limited by model mismatch because the form of the geoacoustic model used in the inversion is always an approximation to the real ocean bottom. The goal of this aspect of the research is to understand the impact of model mismatch on inferences that are made about issues such as dispersion of sound in marine sediments from the results of inversions.The project will use data from previous experiments. New knowledge from this project will: (1) provide confidence in waveform modeling of sound sources used in geoacoustic inversion; (2) provide new information about the impact of neglect of shear wave losses; and (3) provide a means to understand the impact of model mismatch in present day geoacoustic inversion methods.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2024
- Source ID
- N000142412373
Entities
People
- Ross Chapman
Organizations
- Office of Naval Research
- United States Navy
- University of Victoria