Seismo-Acoustic Detection, Localization and Characterization if Ice-Mechanical Events in Arctic Sea Ice
Abstract
To facilitate planning of an observation campaign building knowledge needed to improve operational prediction of Arctic sea ice. MIT will work with Woods Hole Oceanographic Institution and other SIDEX partners on the moniitoring and characterization of ice-mechanical events in Arctic sea ice using acoustic and seismic arrays deployed on or below the ice cover in concert with non-acooustic stress and strain sensors deployed by the partners. The emphasis of the MIT effort will be 1. High-fidelity Modeling of Ice-Mechanical Seismo-Acoustic Emission MIT will upgrade its legacy OASES model for 3D radiation and propagation of seismo-acoustic waves in and below the ice cover for realistic assessment of the propagation of acoustic emission from various modes of ice fractures and post-fracture processes in the thinning Arctic ice sheet to support accurate localization and characterization of ice events with strong radiation directionality in stratified shallow and deep water environments. Being based on the wellestablished legacy OASES stratification modeling approach, n addition to the ice elasticity, the models will provide realistic representations of the bottom interaction, even in extremely shallow water of the early SIDEX experiments. Specific upgrades will include the seismic coupling across ice floe boundaries which past experiments showed being extremely important due to strong coupling between longitudinal and vertically and horizontally polarized Lamb and Love modes, propagating at distinctly different speeds. Another important is the incorporation of vertical anisotropy in the ice sheet, again affecting both the radiation and the propagation characteristics. 2. Seismo-Acoustic Array Design and Deployment MIT will use the 3D OASES modeling infrastructure for the optimal design of the seismic and acoustic arrays to be deployed in the shallow and deep water Arctic environments, and will actively participate in the deployment and testing of the arrays during the SIDEX field efforts. 3. Seismic Event Localization Based on its experience with ice event localization using geophone and hydrophone arrays during extended deployments in the ONR SIMI93 and SIMI94 ice camp experiments, MIT will upgrade and utilize its legacy array processing approaches for event location, incorporating the seismic coupling between wave types at the floe boundaries and the distinct radiation patterns of the various fracture and deformation modes. 4. Seismic Event Characterization In connection with the SIMI93 and SIMI94 experiments, MIT has developed high-fidelity bphysics-based models for the directionality of the source generation and propagation of the seismic wavefield in the ice cover and its 3D coupling into acoustic waves in the stratified water column and seabed. These models will be utilized for characterizing and classifying the ice events using seismic first-motion analysis. In contrast to the earlier experiments, a comprehensive stress and strain measurement suite will be available in SIDEX, which in combination with the analysis of the acoustic emission will enable the development of a vastly improved understanding of the dominant mechanical processes involved in the ice mechanics and dynamics under environmental stress.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2019
- Source ID
- N000141912607
Entities
People
- Henrik Schmidt
Organizations
- Massachusetts Institute of Technology
- Office of Naval Research
- United States Navy