Delineation of a temperate glacier bed using 3D migration

Mark L. Moran; Steven A. Arcone; Allan J. Delaney; Roy J. Greenfield

doi:10.1117/12.383569

27 April 2000 Delineation of a temperate glacier bed using 3D migration

Mark L. Moran, Steven A. Arcone, Allan J. Delaney, Roy J. Greenfield

Proceedings Volume 4084, Eighth International Conference on Ground Penetrating Radar; (2000) https://doi.org/10.1117/12.383569
Event: 8th International Conference on Ground Penetrating Radar, 2000, Gold Coast, Australia

Abstract

We have defined the complex bed topography for a section of a small temperate glacier using 50-MHz monostatic short-pulse radar data and a synthetic aperture array processing method. The data were collected on a 100- by 340-m array grid in the upper stem of the Gulkana Glacier of central Alaska. The array processing was based on a modified 3-D Kirchhoff migration integral and implemented with a synthetic aperture approach that uses sequences of overlapping subarrays to generate depth images in vertical planes. Typical subarray beam widths are generally less than 5 degrees at the -6-dB level, giving a flashlight-like searching capability without distorting the wavelet shape. The bed topography was constructed uscg specular reflections picked from 3-D array depth images. In some instances reflections were imaged outside the data coverage area. The bed surface dips steeply, both parallel and transverse to the direction of ice flow. The maximum observed depth is roughly 140 m. The 3-D method resolved bed dips up to 45 degrees. In regions of steepest dip, it improved depth accuracy by 36% compared it raw data, and by 15% compared with standard 2-D migration. Over 12 dB of signal-to-noise improvement and improved spatial resolution were achieved compared to raw data and 2-D migration. False bottom layering from out-of-plane arrivals, seen in the raw data and in 2-D migrations, are not observed in the 3-D array results. Furthermore, loss of bottom reflections are shown by the 3-D migration to be attributable to the dip and curvature of the reflector, and not scattering losses or signal clutter from englacial inclusions.

Citation Download Citation

Mark L. Moran, Steven A. Arcone, Allan J. Delaney, and Roy J. Greenfield "Delineation of a temperate glacier bed using 3D migration", Proc. SPIE 4084, Eighth International Conference on Ground Penetrating Radar, (27 April 2000); https://doi.org/10.1117/12.383569

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