Active Seismic Refraction, Reflection, and Surface-Wave Surveys in Thick Debris-Covered Glacial Environments

Debris-covered glaciers (DCG) and 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 buried ice features on planetary bodies such as Mars. Characterizing the supraglacial debris layer is a large part of these efforts. Geophysical exploration of DCG 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 DCG using the Sourdough Rock Glacier in Southcentral Alaska as a test site. We provide evidence for imaging an ultra-shallow seismic reflection from the bottom of the loose debris layer using ultra-dense receiver arrays and compare it to ground-penetrating radar (GPR) images taken along the same profiles. We also detail how reliable dispersion curve images can be extracted from the surface wave package of the seismic data using the multi-channel analysis of surface waves technique, which allows for the (s)-wave profile to be inverted for. We find this could be a valuable addition to the toolbox of future geophysical investigations on DCG. Debris-covered glaciers and rock glaciers are glaciers with a loose rock layer covering all or most of their surface. This layer can be several meters thick and plays an important role in how fast the glacier melts. These types of glaciers are an important analog to similar buried ice features observed on other planetary bodies, such as Mars. Typically, the subsurface of these glaciers is studied using the geophysical method of ground-penetrating radar (GPR), though in this paper we explore how active-source seismic methods could be utilized in future surveys. We demonstrate that using active-seismic techniques can provide information on the "stiffness" of the debris layer, which can add context to a GPR survey and ultimately aid in interpreting glacial features. We use ultra-dense receiver spacing to image a seismic reflection from the bottom of the loose debris layer on a debris-covered glacierWe demonstrate that we can obtain the shear-wave velocity structure (stiffness) observations for debris cover on glaciers