Active Seismic Refraction, Reflection and Surface-Wave Exploration in Debris-Covered Glacial Environments, Sourdough and Malaspina Glaciers, Alaska

Abstract

Debris-covered glaciers, otherwise known as rock glaciers, have been increasingly studied in recent years because of the role they play within local watersheds, glacial ablation models due to climate change, and as analogs for debris-covered glaciers on planetary bodies such as Mars. Characterizing the supraglacial debris layer is a large part of these efforts. Geophysical exploration of debris-covered glaciers has mostly excluded active seismic methods, with the exception of refraction studies, due to the attenuating properties of the debris cover and field survey efficiency. We evaluate the accuracy, field efficiency, and effectiveness of seismic refraction, reflection, and surface wave surveys for determining the elastic properties of the debris layer and any underlying layers on Sourdough Rock Glacier as well as sites in the Malaspina Glacier forelands. We compare our results with ground-penetrating radar. For the first time, we image an ultra-shallow seismic reflection from the bottom of the loose debris layer using ultra-dense receiver arrays. This study also presents the first results using multi-channel analysis of surface waves (MASW) on a rock glacier. The MASW results highlight the variability of the shear-wave structure within the debris layer and are able to capture zones of low velocity.