Imaging an object buried in the sediment bottom of a deepsea by linearized inversion of synthetic and experimentalscattered acoustic wavefields

Abstract

This paper is concerned with the reconstruction, from measured(synthetic and experimental) data, of a 2D penetrablefluid-like cylindrical object of arbitrary cross-sectionimbedded in a fluid-like (sediment) half-space separated by aplane interface from another fluid half-space (deep water)wherein propagates a plane acoustic interrogating wave. The Greentheorem is used to provide (1) a domain integralrepresentation (DIR) of the scattered field and (2) a domainintegral equation (DIE) for the pressure field in a test regioncontaining the object. Both the DIE and DIR are discretized bycollocation, thereby leading to a linear system of equationsfor the discretized pressure in the test region and a lineartransform for the discretized pressure outside the test region.This is the means adopted herein for generating syntheticscattered field data. The inverse problem is linearized byreplacing the (unknown) field in the test region by the (known)field which is established in the water/sediment system in theabsence of the object. Using this Born approximation andminimizing the discrepancy between the measured and modelscattered fields gives rise to a linear system of equationsfor the (unknown) discretized index-of-refraction contrastfunction in the test region. Due to its ill conditioned nature,the linear system is solved by a singular value decompositiontechnique. Images of the index-of-refraction contrastrepresentation of the object obtained by inversion of bothsimulated and experimentally measured scattered field data arepresented and compared.