scholarly journals Assessing Ground Penetrating Radar's Ability to Image Subsurface Characteristics of Icy Debris Fans in Alaska and New Zealand

2018 ◽  
Vol 23 (4) ◽  
pp. 423-436 ◽  
Author(s):  
Robert W. Jacob ◽  
Jeffrey M. Trop ◽  
R. Craig Kochel
Keyword(s):  
New Zealand ◽  
Ground Penetrating Radar ◽  
Transverse Electric ◽  
Transverse Magnetic ◽  
Glacial Ice ◽  
Signal Velocity ◽  
Alpine Regions ◽  
Flow Processes ◽  
Ground Penetrating ◽  
Antenna Polarization

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings collected in 2013 indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice.

scholarly journals Ground-penetrating radar theory and application of thin-bed offset-dependent reflectivity

Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. K47-K57 ◽  
Author(s):  
John H. Bradford ◽  
Jacob C. Deeds
Keyword(s):  
Ground Penetrating Radar ◽  
Transverse Electric ◽  
Transverse Magnetic ◽  
Stratified Medium ◽  
Contaminated Site ◽  
Amplitude Variation ◽  
Amplitude Variation With Offset ◽  
Avo Analysis ◽  
Characteristic Wavelength ◽  
Ground Penetrating

Offset-dependent reflectivity or amplitude-variation-with-offset (AVO) analysis of ground-penetrating radar (GPR) data may improve the resolution of subsurface dielectric permittivity estimates. A horizontally stratified medium has a limiting layer thickness below which thin-bed AVO analysis is necessary. For a typical GPR signal, this limit is approximately 0.75 of the characteristic wavelength of the signal. Our approach to modeling the GPR thin-bed response is a broadband, frequency-dependent computation that utilizes an analytical solution to the three-interface reflectivity and is easy to implement for either transverse electric (TE) or transverse magnetic (TM) polarizations. The AVO curves for TE and TM modes differ significantly. In some cases, constraining the interpretation using both TE and TM data is critical. In two field examples taken from contaminated-site characterization data, we find quantitative thin-bed modeling agrees with the GPR field data and available characterization data.

scholarly journals Imaging the structure of cave ice by ground-penetrating radar

2011 ◽  
Vol 5 (2) ◽  
pp. 329-340 ◽  
Author(s):  
H. Hausmann ◽  
M. Behm
Keyword(s):  
Electromagnetic Wave ◽  
Internal Structure ◽  
Liquid Water ◽  
Ground Penetrating Radar ◽  
Wave Speed ◽  
Liquid Water Content ◽  
Thin Layers ◽  
Ice Formation ◽  
Alpine Regions ◽  
Ground Penetrating

Abstract. Several caves in high elevated alpine regions host up to several meters thick ice. The age of the ice may exceed some hundreds or thousands of years. However, structure, formation and development of the ice are not fully understood and are subject to relatively recent investigation. The application of ground-penetrating radar (GPR) enables to determine thickness, volume, basal and internal structure of the ice and provides as such important constraints for related studies. We present results from four caves located in the Northern Calcareous Alps of Austria. We show that the ice is far from being uniform. The base has variable reflection signatures, which is related to the type and size of underlying debris. The internal structure of the cave ice is characterized by banded reflections. These reflection signatures are interpreted as thin layers of sediments and might help to understand the ice formation by representing isochrones. Overall, the relatively low electromagnetic wave speed suggests that the ice is temperate, and that a liquid water content of about 2% is distributed homogenously in the ice.

Ground-penetrating radar monitoring of fast subsurface processes

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. A19-A23 ◽  
Author(s):  
Niklas Allroggen ◽  
Daniel Beiter ◽  
Jens Tronicke
Keyword(s):  
Ground Penetrating Radar ◽  
Preferential Flow ◽  
Temporal Dynamics ◽  
Time Lapse ◽  
Monitoring Methods ◽  
Attribute Analysis ◽  
Accessible Information ◽  
Spatial And Temporal Dynamics ◽  
Flow Processes ◽  
Ground Penetrating

Earth and environmental sciences rely on detailed information about subsurface processes. Whereas geophysical techniques typically provide highly resolved spatial images, monitoring subsurface processes is often associated with enormous effort and, therefore, is usually limited to point information in time or space. Thus, the development of spatial and temporal continuous field monitoring methods is a major challenge for the understanding of subsurface processes. We have developed a novel method for ground-penetrating-radar (GPR) reflection monitoring of subsurface flow processes under unsaturated conditions and applied it to a hydrological infiltration experiment performed across a periglacial slope deposit in northwest Luxembourg. Our approach relies on a spatial and temporal quasicontinuous data recording and processing, followed by an attribute analysis based on analyzing differences between individual time steps. The results demonstrate the ability of time-lapse GPR monitoring to visualize the spatial and temporal dynamics of preferential flow processes with a spatial resolution in the order of a few decimeters and temporal resolution in the order of a few minutes. We observe excellent agreement with water table information originating from different boreholes. This demonstrates the potential of surface-based GPR reflection monitoring to observe the spatiotemporal dynamics of water movements in the subsurface. It provides valuable, and so far not accessible, information for example in the field of hydrology and pedology that allows studying the actual subsurface processes rather than deducing them from point information.

Cold–temperate transition surface and permafrost base (CTS-PB) as an environmental axis in glacier–permafrost relationship, based on research carried out on the Storglaciären and its forefield, northern Sweden

2017 ◽  
Vol 88 (3) ◽  
pp. 551-569 ◽  
Author(s):  
Wojciech Dobiński ◽  
Mariusz Grabiec ◽  
Michał Glazer
Keyword(s):  
Ground Penetrating Radar ◽  
Cold Climate ◽  
Northern Sweden ◽  
Climatic Fluctuation ◽  
Glacial Ice ◽  
Empirical Ground ◽  
Glacial Environments ◽  
Transition Surface ◽  
Ground Penetrating ◽  
Tomography Data

AbstractHere, we present empirical ground penetrating radar (GPR) and electroresistivity tomography data (ERT) to verify the cold-temperate transition surface-permafrost base (CTS-PB) axis theoretical model. The data were collected from Storglaciären, in Tarfala, Northern Sweden, and its forefield. The GPR results show a material relation between the glacial ice and the sediments incorporated in the glacier, and a geophysical relation between the “cold ice” and the “temperate ice” layers. Clearly identifying lateral glacier margins is difficult, as periglacial and glacial environments frequently overlap. In this case, we identified areas showing permafrost aggradation already under the glacier, particularly where the CTS is replaced by the PB surface. This structure appears as a result of the influence of a cold climate over both the glacial and periglacial environments. The results show how these surfaces form a specific continuous environmental axis; thus, both glacial and periglacial areas can be treated uniformly as a specific continuum in the geophysical sense. Similarly, other examples previously described also allow identifying a continuation of permafrost from the periglacial environment onto the glacial base. In addition, the ERT results show the presence of double-layered periglacial permafrost, possibly suggesting a past climatic fluctuation in the study area.

Complex internal architecture of a debris-flow deposit revealed using ground-penetrating radar, Cass, New Zealand

2013 ◽  
Vol 69 (1) ◽  
pp. 26-38 ◽  
Author(s):  
Colette C.A. Starheim ◽  
Christopher Gomez ◽  
Justin Harrison ◽  
Claire Kain ◽  
Nicholas J. Brewer ◽  
...  
Keyword(s):  
New Zealand ◽  
Debris Flow ◽  
Ground Penetrating Radar ◽  
Debris Flow Deposit ◽  
Flow Deposit ◽  
Ground Penetrating ◽  
Internal Architecture
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