A SEISMIC REFLECTION STUDY ON THE ABLATION AREA OF THE TAKU GLACIER, SOUTHEAST ALASKA

Abstract:

Active-source seismic reflection techniques have been frequently used to document temporal

and spatial variability in subglacial conditions beneath the ice sheets. Seismic surveys may

provide the topography of the subglacial landscape as well as information about the properties

of subglacial sediments and water. The former is achieved by standard 2D seismic imaging,

the latter by amplitude analysis of the base-ice reflection. Seismic techniques for subglacial

characterization have not yet been fully explored on mountain glaciers, where the ice is

warmer and more attenuative to seismic energy, and the area available for survey is often more

restrictive.

In March 2014 we collected a high-resolution seismic reflection survey on the lower ablation

area of the Taku Glacier in South-East Alaska. The survey line was composed of 120 geophones

buried 0.5 m in the snowpack and spaced by 5 meters. The surface of the glacier was covered by

a spatially variable 2-6 m thick snow cover. Shots, 99 charges of the binary explosive kinepak

(152 grams), were drilled to 6 meters below surface.

We present preliminary seismic images, attenuation estimates and amplitude analysis as well as

a discussion of the challenges of seismic studies in the ablation area of large mountain glaciers

where spatially variable snowpack, rough topography and hidden crevasses hamper standard

seismic interpretation and render successful data interpretation more difficult.