Ocean Acoustic Inversion

海洋声学反演

• 批准号: RGPIN-2014-03629
• 负责人: Dosso, Stan
• 金额: $ 2.19万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=565990
• 关键词: Ocean; Acoustic; Inversion

Oceans are opaque to electromagnetic radiation but transparent to sound; hence, scientists have devised many methods to use acoustics underwater instead of light, radio or microwaves. The remote acoustic sensing of seabed properties/processes or the locations of sound sources (e.g., submarines, marine mammals) are important problems with geological, geotechnical, environmental and defence applications. However, acoustic remote sensing requires solving a nonlinear inverse problem which is inherently non-unique with uncertainties and resolution that are often not well understood. The proposed research builds on our work in theory and applications of quantitative Bayesian (probabilistic) inversion for ocean-acoustic remote sensing and related seismic problems with several projects. (1) Inversion for seabed acoustic scattering parameters and processes. Our initial work shows that inversion of acoustic backscatter data can resolve in-situ seafloor roughness and sediment heterogeneity spectra (a remote-sensing alternative to laborious direct measurements). We propose to develop quantitative model-selection approaches to determine the relative importance of various physical scattering mechanisms and to estimate relevant scattering parameters and uncertainties for different seabed types, to better understand the physics of seabed scattering and advance geoacoustic databases and sonar models. (2) Estimation of laterally-variant seabed scattering and geoacoustic parameters for naval databases or geotechnical applications such as cable-laying. This approach is based on sequential Bayesian inversion of novel acoustic data sets collected along a track using a mobile system comprising an acoustic source and receiver array towed near the seabed by an autonomous underwater vehicle. (3) Tomographic (2D) inversion for seabed geoacoustic properties using full-field acoustic data recorded at a fixed receiver array. A major component of quantitative nonlinear inversion in 2D involves developing new self-adaptive sparse/irregular numerical grids to parameterize the environment in a manner consistent with the resolving power of the data. (4) Acoustic source localization and uncertainty estimation, including the effects of uncertainty in ocean environmental properties. Our initial work was in naval (passive sonar) applications, but we are moving into marine-mammal studies in collaboration with JASCO Research Ltd, a leading Canadian marine-technology company. New methods include a novel approach to matched-field localization with non-synchronized array systems/sub-systems, and source ranging via modal dispersion (time-frequency analysis) at a single receiver. (5) Tracking an unknown number of vocalizing marine mammals using long-term acoustic monitoring data. This requires developing a Bayesian tracking algorithm to sample over the number of mammals and their tracks, constrained by prior information on swim speed, and provide a probabilistic solution from which information on population and behaviour can be extracted. (6) Passive seismic inversion for crustal/tectonic structure of Cascadia (Canada’s highest earthquake/tsunami hazard), in collaboration with the Geological Survey of Canada. This involves developing a joint tomographic inversion of teleseismic data (receiver functions) and ambient seismic noise (surface-wave dispersion) to resolve 2D structure which can be correlated with historical earthquake foci. The transition from subduction to transform faulting at the Queen Charlotte margin is of particular interest given the 2012 magnitude 7.8 earthquake and local tsunami, and ocean-bottom seismometers from the NEPTUNE system provide new mid-plate data for a section across the Juan de Fuca plate and Cascadia subduction zone.

海洋对电磁辐射是不透明的，但对声音是透明的;因此，科学家们设计了许多方法来使用水下声学而不是光，无线电或微波。海底属性/过程或声源位置的远程声学传感（例如，潜艇、海洋哺乳动物）是地质、岩土工程、环境和国防应用的重要问题。然而，声学遥感需要解决一个非线性逆问题，这是固有的非唯一的不确定性和分辨率，往往没有很好地理解。拟议的研究建立在我们的工作的理论和应用定量贝叶斯（概率）反演海洋声学遥感和相关的地震问题与几个项目。(1)海底声散射参数和过程的反演。我们的初步工作表明，声波后向散射数据的反演可以解决现场海底粗糙度和沉积物异质性谱（遥感替代费力的直接测量）。我们建议开发定量模型选择方法，以确定各种物理散射机制的相对重要性，并估计相关的散射参数和不确定性，为不同的海底类型，以更好地了解海底散射的物理和先进的地质声学数据库和声纳模型。 (2)用于海军数据库或岩土工程应用（如电缆铺设）的横向变化海底散射和地声参数的估计。这种方法是基于新的声学数据集的顺序贝叶斯反演收集沿着使用移动的系统的轨道，包括一个声源和接收器阵列拖在海底附近的自主水下航行器。(3)利用固定接收器阵列记录的全场声学数据进行海底地声特性的层析成像（2D）反演。定量非线性反演的一个主要组成部分，在2D涉及开发新的自适应稀疏/不规则的数值网格参数化的环境中的方式一致的数据的分辨率。(4)声源定位和不确定性估计，包括海洋环境特性不确定性的影响。我们最初的工作是在海军（被动声纳）的应用，但我们正在与加拿大领先的海洋技术公司JASCO研究有限公司合作，进入海洋哺乳动物研究。新方法包括使用非同步阵列系统/子系统进行匹配场定位的新方法，以及通过单个接收器处的模式色散（时频分析）进行源测距。(5)利用长期声学监测数据追踪数量未知的发声海洋哺乳动物。这需要开发一种贝叶斯跟踪算法，对哺乳动物及其轨迹的数量进行采样，并提供一种概率解决方案，从中可以提取有关种群和行为的信息。(6)与加拿大地质调查局合作，对卡斯卡迪亚（加拿大最严重的地震/海啸灾害）的地壳/构造结构进行被动地震反演。这涉及到开发一个联合层析反演的地震数据（接收器功能）和环境地震噪声（表面波色散），以解决二维结构，可以与历史地震震源。鉴于2012年发生的7.8级地震和当地海啸，夏洛特女王边缘从俯冲到转换断层的转变特别令人感兴趣，NEPTUNE系统的海底地震仪提供了新的中板数据胡安·德富卡板块和卡斯卡迪亚俯冲带的部分。