Broadband synthetic aperture matched field geoacoustic inversion with a single hydrophone

Abstract

Traditionally matched-field geoacoustic inversion experiments sampled the acoustic field on long arrays and require powerful transmissions in order to reduce parameter uncertainty. However, single-hydrophone based geoacoustic inversion methods exist. Practically, these methods are attractive compared to the ones using long arrays. In a single hydrophone setup, spatial diversity is traded off for frequency diversity; the source is broadband. This paper uses single-hydrophone frequency coherent matched-field inversion and exploits extended-duration coherent transmissions (multiple LFM chirps) to increase signal to noise ratio. As a result, the overall signal becomes Doppler/motion intolerant. But Doppler can be modeled by including source and hydrophone horizontal motions. To correlate well with the measured field across a receiver trajectory and to incorporate a transmission across source trajectory, Doppler in waveguide and normal mode theory are applied. The method is demonstrated with 100-900 Hz LFM SW06 data with low signal to noise ratio.