Three-dimensional acoustic localization in the arctic using an ice-mounted geophone

Abstract

This paper presents an approach to three-dimensional (3-D) localization of an acoustic source in the water column using a single three-component geophone mounted on the surface of Arctic sea ice. Source bearing is estimated by computing the received signal power as a function of horizontal look angle, applying seismic polarization filters to suppress ice shear waves with transverse particle motion. The inherent 180° ambiguity is resolved by considering vertical-radial particle motion, providing a unique bearing estimate. Source range and depth are estimated from arrival-time differences of the direct water-borne acoustic wave and ice seismic waves including the longitudinal plate mode and horizontally-polarized shear mode. This produces a system of two quadratic equations in two unknowns (range and depth) which admits two solutions, one of which corresponds to the correct source location; the secondary solution is often at an unphysical depth. The 3-D localization approach is applied to seismo-acoustic recordings collected on smooth and rough/ridged annual ice and on a multi-year ice floe. The results indicate good 3-D localization over the limited range over which first-break arrivals of the ice seismic waves could be reliably detected.